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SWINGLE'S CATECHISM 

OF 

Steam, Gas, and Electeic 
Engineering 



A complete Practical System of Instruction covering all 
the important details relative to the care and operation of 
Steam Boilers, Steam Engines, Steam Turbines, Air 
Compressors, Refrigerating Machinery, Elevators — both 
Electric and Hydraulic, also Electric Machinery, in- 
cluding Dynamos, Motors, Transformers, Rotary Con- 
verters, Switch Boards, etc. 



Especially valuable to those contemplating an ap- 
pearance before an Examining Board of Engineers 

A Complete Book of Reference for the 

Working Engineer in the daily 

round of his duties. 

BY 

CALVIN F. SWINGLE 

Author of "Twentieth Century Hand &ook for Steam Engineers and 

Electricians." "Encyclopedia of Engineering," 

and "Steam Turbine Engines." 




CHICAGO 

FREDERICK J. DRAKE & COMPANY 

PUBLISHERS 



<**!* 






Copyrigtit 1922, 1D17 and 1910 

By 
Frfdebick J. Drake & Co. 



® C1AC86294 

Printed in U. S. A. 



OCT 16 72 



Swingle's Catechism of Steam, Gas, 
and Electrical Engineering 



INTRODUCTION 

The constantly increasing demand for information in a 
condensed form, pertaining to engineering topics has in- 
duced the author to prepare this book, with a view of 
assisting his brother engineers in their search for just the 
information that they are looking for, and especially when 
they are in a hurry, and do not have much time to look 
for it, as, for instance, in an emergency due to a break- 
down, the Catechism of Steam, Gas, and Electricity will be 
found to be an invaluable aid, for the reason that it covers 
practically the entire field of Stationary Engineering, in- 
cluding not only Steam Boilers and Engines, but, in addi- 
tion, Steam Turbines, Gas Engines, and Gas Producers, 
Air Compressors, Eefrigeration and Ice Making, Elevators, 
both Electric and Hydraulic, and finally, the subjects of 
Electricity and Electric Machines, Dynamos, Motors, etc, 

The necessity for thorough and complete examinations 
regarding the qualifications of men asking to be entrusted 
with the care and operation of power generators, whether 
steam, gas or electrical, is now universally recognized, and 
as a consequence, all large cities and towns, and a large 
number of states, have license laws, requiring engineers and 
electricians to pass these examinations before being granted 
license permitting them to take charge of and operate such 



Introduction 

machinery. To those contemplating the taking of such ex- 
aminations, the questions and answers following will prove 
to be a most valuable helper, as it furnishes the much 
sought-f or information in plain, easily understood language*, 
the answers being condensed in such form as to enable the 
applicant for license to memorize them without any diffi- 
culty whatever, and thus be able to qualify himself for the 
position sought for. This Catechism thus serves the double 
purpose of being an assistant to the working engineer, and 
also a helper to the man who aspires to become an engineer. 

Calvin F. Swixgle. 



Types of Boilers 



1. TV^at types of boilers are most commonly used for 
stationary work? 

Ans. The horizontal tubular boiler and the water-tube 
boiler. 

2. Describe in general terms the horizontal tubular 
boiler. 

Ans. It consists of a shell having tubes of small diam- 
eter, extending from head to head. 

These tubes are located in the water space. 

3. What is their function? 

Ans. To supply a passageway to the stack for the hot 
gases from the furnace. 

4. Does the water in. the boiler receive heat from these 
tubes ? 

Ans, It certainly does. 

5. Describe the route taken by the smoke and hot 
gases in the operation of a tubular boiler. 

Ans. From the furnace, located under the front end 
of the boiler, the gases pass under and along the sides of 
the shell, back to the rear end, the upper part of which is 
arched over. The route is here reversed, and the products 
of combustion return through the flues towards the front 
end and thence through the breeching into the stack. 

6. Is this type of boiler economical in the burning of 
fuel? 

Ans. It can be made so if properly set and handled in 
operation. 

7. Describe in a general way the water-tube boiler. 
Ans. It consists of a set, or sets of tubes 3 to 4 inches 

in diameter, sometimes vertical, and sometimes inclined, 

5 



6 Steam Engineering 

and connected at the top to a steam drum, and at the bot- 
tom to a mud drum. 

8. What advantages as regards circulation of the water 
has the water tube boiler? 

Ans. It provides for a free circulation. 

9. Name another advantage connected with the water 
tube boiler. 

Ans. The margin of safety from dangerous explosions. 

10. Why is this? 

Ans. Because if one or more tubes gives way the pres- 
sure is relieved. 

11. What precautions should be observed in the design 
and construction of a boiler? 

Ans. The best materials should be used, the boiler 
should be simple in design, and the workmanship should be 
perfect. 

12. Where should the mud drum be located ? 

Ans. In a place removed from the action of the fire. 

13. What should be the capacity of the boiler relative 
to its work ? 

Ans. It should have a steam and water capacity suf- 
ficient to prevent any fluctuation in either the steam pres- 
sure, or the water level, if properly fed. 

14. Why should the water in a boiler circulate freely 
and constantly ? 

Ans. In order to maintain all parts at as near the same 
temperature as possible. 

15. What should the strength of a boiler be, relative to 
the strain it is liable to be subject to? 

Ans. It should have a great excess of strength, 

16. Is a combustion chamber an advantage to a boiler? 



Types of Boilers 7 

A ns. It is, in order to complete the combustion of the 
gases before they escape to the cliimney. 

17. How should a boiler be arranged with regard to 
cleaning? 

Ans. All parts should be easily accessible for cleaning 
and repairs. 

18. What type of boiler is the Cahall? 
Ans. It is a water-tube boiler. 

19. Is it vertical or horizontal? 
Ans. It is built either way. 

20. What form of Cahall is generally used in cental! 
power stations? 

Aiis. The horizontal form. 

20a. What is the range of pressures that these boilerr 
are built for? 

Ans. From 160 to 500 pounds per square inch, 

21. Describe the method of constructing the joints. 
Ans. The sheets are beveled on the edges, bent intc 

shape, and rivet holes drilled after bending. 

22. What is gained by so doing? 

Ans. Absolutely round rivet holes and no crystalliza 
tion. 

23. What type of riveted joint is used on the highe* 
pressure boilers? 

Ans. Triple riveted, double strapped. 

24. How are the tubes connected to the steam druitf 
in the Cahall boiler? 

Ans. By nipples connected to saddles on the drum. 

25. Does this boiler rest upon the brick work? 

Ans, It does not, but is suspended free from the ma 
sonry. 

26. What advantage is there in this style of setting? 



f 

8 Steam Engineering 

Ans. The entire structure is free to expand or contract 
without causing any strains on either boiler or brick work. 

27. Describe the Heine boiler. 

Ans. It consists of one, and sometimes two shells or 
drums resting upon water legs riveted to each end. These 
water legs are connected by horizontal tubes. The water 
fills the tubes, water legs, and partially fills the shell, leav- 
ing the upper portion for steam space. 

28. In the setting does this boiler occupy a horizontal 
position ? 

Ans. No. The shell and tubes have an incline of one 
inch in twelve from front to rear. 

29. What provision is made for cleaning and repairing 
the tubes ? 

Ans. Hand-holes are located in the head plates oppo- 
*ite each tube. 

30. How are these hand-holes closed? 
Ans. In the ordinary way, by plates. 

31. Where is the mud drum located in the Heine boiler ? 
Ans. Inside the shell, near the bottom. 

32. How is the Heine boiler supported in the setting? 
Ans. The front or fixed end rests upon cast iron col- 
umns. The rear water leg upon rollers. 

33. Describe in brief the Babcock & Wilcox boiler. 
Ans. It is composed of wrought iron tubes, placed in 

an inclined position, and connected with each other, and 
with a horizontal steam, and water drum by vertical headers. 

34. Where is the mud drum in this boiler ? 

Ans. In the rear, and connected to the lowest part of 
the boiler. 

35. What provision is made for cleaning the tubes in 
the Babcock & Wilcox boiler? 



Types of Boilers 9 

Ans. Through hand-holes in the headers, opposite each 
tube. 

36. How is this boiler supported in the setting? 

Arts. It is suspended from wrought iron girders, en- 
tirely independent of the brick work. 

37. Describe in general terms the Stirling boiler, 
Ans. It consists of three upper steam drums, each be- 
ing connected by a number of tubes to a lower or mud 
drum. 

38. How are the steam spaces connected? 
Ans. By shorter tubes. 

39. How is the boiler supported? 
Ans. On a structural steel frame work. 

40. What provision is made for expansion and contrac- 
tion of the tubes ? 

Ans. They are slightly curved near the ends. 

41. How are the hot gases directed in their course 
from furnace to stack ? 

Ans. By means of fire brick baffle walls. 

42. How is the interior of this boiler cleaned? 

Ans. Four manholes are provided in the drums, by 
which access to the interior of both the drums and tubes is 
obtained. 

43. What type of boiler is the Maxim boiler? 

Ans. It is a water-tube boiler consisting of two drums, 
one above the other, connected by tubes. 

44. Describe the tubes. 

Ans. Each tube has two bends, thus providing for un- 
equal expansion or contraction. 

45. How is the heating surface of the Maxim boiler 
arranged ? 



10 Steam Engineering 

Ans. It is so arranged that the current of heated gases 
is made to travel three times the length of the tubes, the 
direction of the current being changed seven times in its 
route from furnace to stack. 

46. What can be said of the Bigelow-Hornsby water- 
tube boiler? 

Ans. Owing to the flexible form of its construction it 
is possible to build it in very large units, 2,000 horsepower 
and upwards. 

47. What peculiar feature makes this possible? 

Ans. Each section is independent of its neighbor, ex- 
cept the nipples connecting with the steam drum, and the 
equalizing nipples connecting the bottom drums of the 
rear sections. 

48. How is the boiler supported ? 
Ans. Entirely from overhead beams, 

49. What percentage of the heating surface do the tubes 
of the front unit comprise? 

Ans. More than 12 per cent. 

50. Where is the feed water first admitted? 
Ans. Into the bottom drum of the rear unit. 

51. Describe the course of the feed water. 

Ans. The feed water is admitted into the bottom drum 
of the rear unit, and is advanced gradually from the coldest 
to the hottest portion of the boiler. 

52. How is the speed of the feed water up the rear unit 
regulated? 

Ans. By the amount of steam generated, ample time 
being permitted for scale forming matter to be deposited 
in the bottom drum of this unit. 

53. Where does the liberation of steam take place ? 
Ans, In the upper drum. 



Types of Boilers 11 

54. What can be said of this boiler regarding the utili- 
zation of the heat? 

Ans, It is baffled so that the products of combustion 
are carried uniformly over the heating surfaces in thin 
layers, the baffle plates serving to guide the gases through in 
substantially uniform passages. 

55. To what factor of safety is the Bigelow-Hornsby 
boiler built ? 

Ans. Five for 200 pounds working pressure. 

56. Describe in brief the Wickes vertical water-tube 
boiler. 

Ans. It consists of two cylinders joined together end- 
ways by straight tubes, and erected in a vertical position. 

57. What can be said of the top cylinder? 

Ans. It is the longer, and is designated the steam drum. 

58. What about the bottom cylinder? 

Ans. It is the shorter, and is designated the mud drum. 
Both cylinders vary in dimensions as to diameter and 
length, according to the power required of the boiler. 

59. Where are the manholes of the Wickes boiler? 
Ans. One is placed in the convex head of the steam 

drum ; there are also a number of hand-holes in this head. 
A manhole is also placed in the lower or mud drum, near 
the floor, thus permitting access to the top and bottom of 
the boiler, 

60. How are these tubes divided ? 

Ans. By heavy fire-clay tile these tubes are divided into 
two compartments. Those tubes in the front compart- 
ment are called the "risers" and those in the rear the 
"downcomers" 

61. What can be said of the heat in its double passage? 



12 Steam Engineering 

Ans. It surrounds completely, and closely the tubes in 
both compartments. 

62. Where is the water line in this boiler? 

Ans. At a sufficient height in the steam drum to in- 
sure the complete submersion of all the tubes. 

63. How is the brick work setting of the Wickes water- 
tube boiler arranged? 

Ans. It is independent of the weight of the boiler, and 
free to expand or contract. 

64. Describe briefly the design of the Atlas water-tube 
boiler'. 

Ans. It consists mainly of three drums and two water 
legs extending crosswise, while the tubes extend lengthwise. 

65. What is the original feature in the design of the 
water legs? 

Ans. They are formed by the continuation of front 
and rear shell plates. 

66. What other valuable feature is claimed for this 
boiler ? 

Ans. After the steam leaves the vessels containing water 
it is passed through a series of superheating tubes, and is 
superheated. 

67. Describe the course of the feed water. 

Ans. It is fed first into the purifier, whence it over- 
flows into the rear drum and down into the rear leg, thence 
through the inclined tubes to the front leg, thence up into 
the front drum, where the steam is liberated and carried 
through superheating tubes to the steam drum. 

68. What are the facilities for cleaning the water tubes 
of this boiler? 

Ans. An individual hand-hole is located opposite each 
end of each water tube. 



Types of Boilers 13 

69. How is the interior of each of the three cross drums 
reached? 

Ans. Through a large manhole in each end. 

70. Describe briefly the design and construction of 
the Marzolf water- tube boiler. 

Ans. It consists of three drums connected with each 
other in triangular form. Drum A directly over the **e 
is connected by tubes with drum B above it, and with drum 
C in the rear and slightly below it. Drum C, which is the 
mud drum, is also connected with drum B. The tubes are 
each slightly bent. The steam is collected in drum B, which 
is maintained about one-third full of water. 

71. Describe in brief the action of the heat upon this 
boiler. 

Ans. It acts first upon the water in drum A over the 
furnace, then by means of a baffle wall it is carried along 
the inclined tubes to drum B, where it is deflected and car- 
ried down along other inclined tubes to drum C, thence to 
the stack. 

71. How are the products of combustion caused to act 
upon the lower bank of tubes? 

Ans. By means of baffle walls located in the rear of 
the furnace. 

72. At what point in this boiler is the feed water ad- 
mitted ? 

Ans. At the lowest point, viz., the mud drum. 

73. What are the principal advantages claimed for the 
Duplex water-tube boiler? 

Ans. Delivery of superheated steam ; the removal of 
steam from the boiler at a point where there is no ebul- 
lition; the dnims not exposed to the direct action of the 
fire. 



14 Steam Engineering 

74. describe in brief the design of this boiler. 

Ans. Two upper steam drums connected by tubes, a 
mud drum at the bottom and rear which is connected to 
the upper drums by headers and short nipples. The tubes 
are inclined 20 degrees to insure rapid and positive cir- 
culation. 

75. How is this boiler supported? 
Ans. Upon a heavy steel framework. 

76. What is the leading feature in connection with 
the Erie City water-tube boiler? 

Ans. The three banks of tubes are practically vertical, 
connected to upper, and lower drums, and spaced so that any 
one of them may be cut out for repairs without interfering 
with the others. 

77. How do the products of combustion act upon this 
boiler ? 

Ans. The baffling is arranged to pass three times across 
the tubes, and at each end of the upper drum is a dry 
chamber. 

78. Describe in brief the best method of supporting 
horizontal tubular boilers. 

Ans. By means of hangers suspended from I beams, 
supported by cast iron columns. This takes the weight off 
the side walls. 

79. What three principles should govern the design 
and construction of steam boilers ? 

Ans. First: They should be absolutely safe. Second: 
They should be economical in the consumption of fuel. 
Third : They should be capable of furnishing dry steam. 

80. What is meant by the term tensile strength as ap- 
plied to boiler material ? 



Types of Boilers 15 ^ 

Arts. The number of pounds of pull that would be 
required to break a bar of the material in the direction of 
its length. 

81. What is liable to occur in case the tensile strength 
is too high? 

Arts. Cracking of the sheets, also certain changes in the 
physical properties of the metal. 

82. Which are the stronger, punched or drilled plates? 

Ans. If the material is good soft steel, punched plates 
show a greater shearing resistance. 

83. What should be the tensile strength of rivet iron? 
Am. About 60,000 pounds per square inch. 

84. What is a good test for a %-inch rivet ? 

Ans. It should stand being doubled up and hammered 
together cold without being fractured. 

85. What is the shearing resistance of iron rivets? 
Ans. About 85 per cent of the original bar. 

86. What is the shearing resistance of steel rivets ? 
Ans. 77 per cent of the original bar. 

87. What is meant by efficiency of the joint? 

Ans. The percentage of strength of the solid plate, that 
is retained in the joint. 

88. What should be the style of joint with sheets thicker 
than y<z inch? 

Ans. It should be a double butt joint. 

89. What should be the ratio of diameter of rivet to 
thickness of plate for double butt joints? 

Ans. The diameter of the rivet should be about J. 8 
times the thickness of sheet. 

90. What should be the pitch of rivets ? 



26 Steam Engineering 

Ans. Three and one-half to four times the diameter of 
the hole. 

91. Describe the triple riveted butt joint. 

Ans. It has two welts or straps, one inside, and one 
outside. 

92. Is this a good form of joint? 
Ans. It is. 

93. What type of joint gives the highest efficiency ? 
Ans. A joint in which the tensile strength of the rod3 

from which the rivets are cut approaches that of the plate?, 
and when the proportions of the joint are such, that the 
tensile strength of the rivets, and the crushing resistance 
of the rivets and plate, for a given, or unit strip, are as 
nearly equal as it is possible to make them. 

94. In how many ways may failure occur in a double 
riveted butt joint? 

Ans. In five distinct ways. 

95. Name the first manner of failure. 

Ans. Tearing of the plate at outer row of rivets. 

96. What is the second ? 

Ans. Shearing two rivets in double shear, and one in 
single shear. 

97. What is the third manner of failure? 

Ans. Tearing of the plate at inner row of rivets, and 
shearing one rivet in the outer row. 

98. Describe the fourth method of failure. 
Ans. Crushing in front of three rivets. 

99. What is the fifth manner of failure? 

Ans. Crushing in front of two rivets, and shearing one. 

100. How may a triple riveted butt joint fail? 



Types of Boilers 17 

Ans. First: By tearing the plate at the outer row of 
rivets. Second: By shearing four rivets in double shear, 
and one in single shear. Third : Eupture of the plate at 
the middle row of rivets, and shearing one rivet. Fourth : 
Crushing in front of four rivets, and shearing one rivet. 

101. What is the efficiency of the quadruple riveted 
butt joint ? 

Arts. In some cases as high as 94 per cent. 

102. In what four ways may failure occur in this type 
of joint? 

Ans. First: By tearing the plate at the outer row of 
rivets. Second : By shearing eight rivets in double shear, 
and three in single shear. Third : By tearing at inner row 
of rivets, and shearing three rivets. Fourth : By tearing at 
first outer row of rivets where the pitch is 7 1 /£ inches. 

103. What is implied in the staying of a flat surface? 
Ans. Holding it against pressure at a series of isolated 

points, which are arranged in symmetrical order. 

104. Does the cylindrical shell of a boiler need bracing? 
Ans. No. 

105. Why is this? 

Ans. Because the internal pressure tends to keep it 
cylindrical. 

106. How are the heads sometimes stayed? 

Ans. By through stay rods of soft steel, or iron l 1 /^ or 
2 inches in diameter extending through from head to head. 

107. What advantage has this form of stays? 
Ans. The pull is at right angles to the plate. 

108. What other methods of bracing the heads of high 
pressure boilers are used? 

Ans. Gusset stays, and dished heads. 



18 Steam Engineering 

109. What is the minimum factor of safety for stays, 
and braces? 

Ans. Eight. 

110. Give a simple rale for finding the bursting pres- 
sure of unstayed fiat surfaces. 

Ans. Multiply the thickness of the plate in inches bt 
ten times the tensile strength and divide the product by 
the area of the surface in square inches. 

110a. What is the rule for finding the safe working 
pressure of a boiler? 

Ans. First calculate the bursting pressure accord- 
ing to the rule given in answer to question 110; then 
divide the result by 5. The quotient will be the safe 
working pressure. 

110b. How should domes be braced? 

Ans. By means of stay rods extending diagonally 
from the sides to the top of the dome. 

110c. Why should the side seams of a boiler be 
stronger than the girth seams? 

Ans. For the reason that the force tending to rup- 
ture the boiler along the line of side seams equals twice 
the stress tending to pull it apart endwise. 



Boiler Setting and Equipment 

111. What two methods of support are generally used 
in the setting of horizontal tubular boilers ? 

Arts. First: By suspension from I beams and girders, 
and secondly by means of brackets riveted to the side sheets, 
and resting upon the side walls. 

112. How are water tube boilers usually supported in 
the setting? 

Ans. By suspension. 

113. What important details should be looked after 
concerning the brick work? 

Ans. The foundations should be good, and the walls 
built in such manner as to take care of the expansion and 
contraction. 

114. How is this accomplished? 

Ans. By leaving an air space of two inches in the side 
and rear walls beginning at the level of the grate bars, and 
extending up to about the center line of the boiler. 

115. What kind of brick should be used for inside 
lining ? 

Ans. Fire brick of good quality. 

116. How should bridge walls be built for horizontal 
tubular boilers? 

Ans. Straight across from wall to wall. 

117. About what distance from the bottom of the boiler 
should this wall be ? 

Ans. Eight to ten inches. 

19 



20 Steam Engineering 

118. Where is the combustion chamber? 
Ans. It is the space back of the bridge wall. 

119. How should boiler walls be secured? 

Ans. By means of tie rods extending the entire length, 
and breadth of the setting. 

120. What are the buck stays? 

Ans. They are strong cast-iron, or wrought-iron bars 
placed vertically upon the outside of the walls, and secured 
to the tie rods. 

121. Should horizontal tubular boilers be set perfectly 
level lengthwise? 

Ans. It is better that they be set about one inch lower 
at the back end, than at the front end. 

122. Give one of the main reasons for this style of 
setting. 

Ans. When washing out the boiler, the mud and water 
will more easily drain towards the blow off pipe. 

123. What is the usual ratio of grate surface to heating 
surface ? 

Ans, One square foot of grate surface to each 36 square 
feet of heating surface. 

124. At what point should the glass water-gauge be 
located ? 

Ans. In such a position as to bring the lowest visible 
portion of the gauge glass exactly on a level with the top of 
the upper row of tubes of a horizontal tubular boiler. With 
other types of boilers the lowest end of the gauge glass 
should always be on a level with the danger point. 

125. Why sEould the above rules be observed in locating 
& water column ? 



Boiler Setting and Equipment 21 

Ans. Because when the water level in the glass begins 
to draw near to the lower end of glass the engineer or water 
tender will have an infallible guide to warn him to get 
busy. 

126. What is a good indication that the connections of 
the water glass are choked or plugged with scale ? 

Ans. When there is no movement of the water in the. 
glass. 

127. Why should there be a trap, or siphon in the pipe 
connecting the steam gauge to the boiler? 

Ans, To prevent the hot steam from coming into con- 
tact with the spring of the gauge. 

128. How may the steam gauge, and safety valve be 
tested in comparison with each other ? 

Ans. By occasionally raising the steam pressure high 
enough to cause the valve to open at the point for which 
it is set to blow. 

129. Is the pop valve reliable as a safety valve? 

Ans. It is, if not allowed to stand idle too long and 
become rusty, 

130. How often should it be allowed to blow off? 
Ans. At least twice a week. 

131. Are lever safety valves used to any extent? 

Ans. They are still in use to some extent, but are rapidly 
being superseded by pop valves. 

132. What is the function of a fusible plug? 

Ans. The fusible alloy of which it is composed will melt 
when it comes in contact with dry steam, and allow the 
steam to blow a warning. 

133. Where is the fusible plug located? 



22 Steam Engineering 

Ans. In that portion of the heating surface of a boiler 
■which is first liable to be overheated from lack of water. 

134. Are Domes and Mud drums necessary parts of 
boilers ? 

Ans. They are not as a rule. 

135. Where should the blow off pipe always be con- 
nected ? 

Ans. With the lowest part of the water space. 

136. Should the blow off cock be opened while the 
boiler is under pressure ? 

Ans. Yes, for a few seconds, once,, or twice each day. 

137. Is a surface blow off any advantage? 
Ans. It is, especially if the water is muddy. 

138. What precautions should be observed with regard 
to inlet for feed water? 

Ans. The feed water should not be allowed to come 
directly in contact with the hot boiler sheets until its 
temperature is equal to, or near that of the water within 
the boiler. 

139. How may this be brought about? 

Ans. By means of feed water heaters, and internal coils 
of pipe through which the feed water is caused to pass. 

140. What is the most economical style of feed pump? 
Ans. The belt-driven power pump. 

141. Is it the most reliable, or safest? 
&n&. It is not. 

^42. What is the most reliable boiler feeding device, for 
all conditions of stationary practice? 
Ans. The double acting steam pump. 



Boiler Setting and Equipment 23 

143. What precautions should be observed in figuring 
on the capacity of a feed pump for a battery of two or 
more boilers? 

Ans. To take into account the total quantity of water 
required by all of the boilers; and let the capacity of the 
pump be equal to it. 

144. In connection with feed apparatus for boilers, 
what other fittings and devices should be installed? 

Ans. There should be a tee located in the horizontal, 
section of the feed pipe near the check valve, and between it 
and the feed pump. One opening of this tee is to be re- 
duced to % or % inch to receive a hot water thermometer 
for testing the temperature of the feed water when making 
evaporative tests, etc. 

145. What other provisions along this line should be 
made? 

Ans. Tanks for weighing the feed water — also a sep- 
arate feed pipe to the boiler under test, also means for 
weighing the coal burned during test. 

146. Is the injector an efficient boiler feeder? 

Ans. It is in locations where there is not very much 
exhaust steam available for heating the feed water. 

147. When, and by whom was the injector invented? 
Ans. In the year 1858, by Henri Giffard. 

148. Why does an injector force water into a boiler 
that is under steam pressure? 

Ans. Because the steam passing through the injector 
imparts sufficient velocity to the water to overcome the 
boiler pressure. 

149. Why does an injector lift water from a lower level ? 



24 Steam Engineering 

Arts. Because the condensation of the steam in the com- 
bining tube creates a vacuum there, and in the suction 
pipe connected with it. 

150. How may the size of the steam header for a battery 
of boilers be determined? 

Ans. The sectional area of the header should equal or 
slightly exceed the sum of the areas of all the boiler outlets 
to be connected with it. 

151. Where should all connections except for drainage, 
enter, and leave the main header? 

Ans. At the top. . 

152. How many valves should there be in each boiler 
connection leading to the header ? 

Ans. Never less than two. 

153. What kind of valves are best for this purpose? 
Ans. Automatic stop, and check valves. 

154. What is the most efficient type of superheater for 
practical purposes? 

Ans. The one that is contained within the boiler setting. 

155. How is the velocity of flow, or piston speed per 
minute of a pump ascertained? 

Ans. Multiply number of strokes per minute by length 
of stroke in feet, or fractions thereof. 

156. The piston speed being known, how is the velocity 
of flow in the discharge pipe found ? 

Ans. The velocity of flow in the discharge pipe is in 
inverse ratio to the squares of the diameters of the pipe and 
the water cylinder of pump. 

157. When it is required to discharge a certain quantity i 
of water from a given size of pipe in a given time, how 
may the velocity of flow in feet per minute be found? 






Boiler Setting and Equipment 25 

Ans. Multiply the number of cubic feet to be discharged 
j by 144 and divide by area of pipe in inches. 

158. When the volume of water to be discharged and 
the velocity of flow are known, how is the area of the pipe 

| obtained ? 

Ans. Multiply volume in cubic feet by 144, and divide 
by velocity in feet per minute. 

159. What is meant by "acceleration of gravity/ 9 and 
what constant number represents it in connection with 
hydraulics ? 

Ans. Acceleration of gravity is the increase in velocity 
caused by the actual weight of the water, and is represented 
by the constant 32. 

160. What per cent of allowance is ordinarily made for 
friction in water pipes? 

Ans. A deduction of 25 per cent is sufficient. 

160a. What is meant by the term ''head in feet" 
when used to designate water pressure? 

Ans. A column of water 2.3 feet in height, or head 
exerts a pressure of 1 lb. per sq. inch at the bottom. 
A pressure of 50 lbs. per sq. inch equals a head in feet 
of 50x2.3, 115 ft. in height. 

160b. What is meant by the term "miner's inch , '? 

Ans. A flow of water equal to* 1.5 cu. ft, or 11.25 
galls, per minute. 

160c. Give the rule for calculating the horse power 
developed by water in falling from a higher to a lower 
level. 

Ans. Multiply number of gallons falling per minute 
by head in feet and divide result by the constant 3970, 

160d. What constitutes 1 water horse power? 



26 Steam Engineering 

Ans. The falling of 3970 galls, a vertical distance 
of 1 ft. in 1 minute of time. 

160e. Give another rule for calculating water horse 
power. 

Ans. Multiply number of galls, falling per minute 
by head in lbs. pressure and divide by 1720. 

160f. What does the constant 1720 represent in the 
above formula? 

Ans. The number of galls, of water which in falling 
a vertical distance of 2.3 ft. (1 lb. pressure) in 1 minute 
of time will exert 1 horse power. 















Feed Water Heaters 

161. Is a feed water heater an economical factor in the 
equipment of a boiler plant? 

Ans. It certainly is, provided exhaust steam is used for 
heating. 

162. How many kinds of exhaust heaters are there? 
Arts, Two, viz.: Open, and closed. 

163. Describe in brief terms the action of a so-called 
open heater. 

Arts. The exhaust steam mingles directly with the 
water, and a portion of it is condensed. 

164. Describe the operation of a closed heater. 

Arts. The exhaust steam and the water are kept sep- 
arate. In some cases the steam passes through tubes that 
| are surrounded by water, and in other types the water 
fills the tube3 that are surrounded by steam. 

165. What difference exists between the two kinds of 
heater ? 

Ans. The closed heater is under full boiler pressure 
when the feed pump is working, while the open heater is 
not because the feed pump is between it and the boiler. 

166. What per cent of saving in fuel may be effected 
by the use of a heater? 

Arts. From 12 to 15 per cent. 

167. Of what capacity should a feed water heater be, 
relative to the boilers ? 

Arts. It should have capacity sufficient to supply the 
boilers for 15 or 20 minutes. 

27 



2g Steam Engineering 

168. Can the exhaust injector be used for feeding 

boilers. 

Ans. It can if the boiler pressure does not exceed i 5 

pounds. 

169. What advantages are gained by the use of mechan- 
ical stokers? 

Ans. Kegulation of the supply of fuel to meet the de- 
mand for steam; also the opening and closing of furnace 
doors is avoided. 

170. What are the disadvantages attending the use of 

mechanical stokers? 

Ans First, cost of installation. Second, in case of a 
sudden demand for steam the mechanical stoker cannot re- 
spond as quickly as in hand firing. Third, extra cost for 
power to operate them. ■. 

171. Into how many classes are mechanical stokers 

grouped ? 
Ans. Four. 

172. Enumerate, and briefly describe. 
Ans. Class one— An endless chain of short grate barsj- 

tliat travel horizontally over sprocket wheels. 

Class two-Grate bars similar to the ordinary type hav- 
ing a continuous motion up and down, or forward and 
back, the bars being either horizontal or slightly mclmed 

Class three— Grate bars steeply inclined and having a 
slow motion. i 

Class f our-Under feed stoker in which the coal is pushed 
up ento the grate by means of a revolving screw, or stean 

ram. , 

173. In what three forms is mechanical draft used fo 

boilers. 



Feed Water Heaters 29 

A ns. First — Induced draft. 

Second — Forced draft, in which fans force air beneath 
the grates. 

Third — A combination of induced and forced draft. 

174. Is a good draft necessary for the efficient opera- 
tion of steam boilers? 

Ans. It certainly is. The economical combustion of 
i fuel cannot be accomplished without a good draft. 

175. For what two purposes are chimneys required? 
Ans. First, to carry off obnoxious gases. Second, to 

create sufficient draft for the combustion of the fuel. 

176. What factor governs the intensity of the drafts 
independent of the dimensions of the chimney? 

Ahs. The difference in weight of the outside and in- 
side columns of air. 

177. What is the best shape of chimney? 
Ans. Round, with a straight flue. 

178. What is the weight, and volume of air at a tem- 
perature of 60°, and under average atmospheric pressure 
at sea level? 

Ans. One cubic foot weighs 536 grains, and 13.06 cubic 
feet weigh one pound. 

178a. Give the composition of pure air. 

Ans. It is a mixture of oxygen and nitrogen, in the 
following proportions: by volume, 20.91 parts oxygen 
to 79.09 parts of nitrogen ; by weight, 23.15 parts oxy- 
gen to 76.85 parts nitrogen. 

178b. Mention an important characteristic of air. 

Ans. It is perfectly elastic, therefore, its density 
and pressure decrease in geometrical ratio with the 
height above the sea level. 



ii 



30 Steam Engineering 

height above the sea level. 

178c. What is the pressure of the atmosphere at an 
altitude of 10,000 feet above sea level? 

Ans. 10.07 lbs. per sq. inch. 

178d. What is atmospheric pressure at an altitude \ 
of 15,000 feet above sea level? 

Ans. 8.32 lbs. per sq. inch. 

178e. What effect does this decrease in atmospheric 
pressure have upon the proportions of boiler furnaces 
and chimneys located in high altitudes? 

Ans. Enlarged proportions and increased capacity ! 
are required to develop the same amount of power as | 
at sea level. 



Care and Operation of Boilers 

179. What is one of the most important duties of the 
'engineer when he goes on watch? 

Ans. To ascertain the exact height of the water in his 
j boilers. 

180. Describe the correct method of doing this. 

Ans. Open the valve in the drain pipe of the water col- 
jumn, and allow the water to blow out freely for a few 
seconds, then close the valve and note the level of the water 
| when it settles back in the gauge glass. 

18 1. What is the next important step in beginning the 
I day's work ? 

Ans. To see that the fires are cleaned, and in good con- 
j dition. 

182. In firing boilers by hand, what is the first and 
most important rule to be observed? 

Ans. Keep a clean fire. 

183. What is the second rule? 

Ans. See that every square inch of grate surface is 
covered with a good live fire. 

184. Give the third rule regarding firing by hand. 
Ans. Keep a level fire. 

185. What is the fourth rule? 

Ans. When cleaning the fire, always clean all clinkers 
and dead ashes away from the back end of the grates and 
the bridge wall. 

31 



32 Steam Engineering 

186. Why should this be done ? 

Ans. In order to allow a free passage of the air through 
the grate bars, so as to promote combustion. 

187. If the plant runs continuously, day and night, 
what is one of the important duties of the fireman coming 
off watch? 

Ans. To leave clean fires, clean ash pits, and a good 
supply of coal ready for the oncoming force. 

188. How long a time should the fires be allowed to 
burn before cleaning? 

Ans. This depends upon the quality of the coal. With 
a coal that does not clinker on the grate bars, an interval 
of 7 or 8 hours may elapse between cleanings, but with the 
average soft coal the fires should not be allowed to burn 
longer than 4 or 5 hours without cleaning. rj 

189. What is one of the greatest aids to good combustion 
in a hand- fed furnace? 

Ans. A clean bridge wall, kept as hot as possible 

190. What precautions should be observed regarding I 
the depth of the fire? 

Ans. It should not be allowed to become so deep and 
heavy as to prevent the air from passing up through it 1 
freely. 

191. How should the position of the ash-pit doors be 
regulated ? 

Ans. With a clean, light fire, a slight opening will be 
sufficient, but with a heavy fire, and the grates clogged with 
ashes, a Larger opening is necessary. 

192. How can the best results be secured in firing 
bituminous coal ? 

Am. By leaving the fire doors slightly open for a few 
secoade immediately after throwing in a fire. 



Care and Operation of Boilers 33 

193. What reason is there for doing this? 

Ans. Because the volatile matter in the coal flashes into 
flame the instant it comes in contact with the heat of the 
turnace, and unless there is sufficient supply of oxygen 
present just then/ the combustion will be imperfect. 

194. What is the result of this imperfect combustion? 

Ans. The formation of carbonic oxide gas, and the con- 
sequent loss of about two-thirds of the heat units contained 
in the coal. 

195. How may this loss be prevented in a great meas- 
ure? 

Ans. By admitting a sufficient volume of air, either 
through the fire doors, directly after throwing in a fresh 
fire, or, better still, providing air ducts through the bridge 
wall, or side walls, which will direct the air in on top of 
the fire. 

196. How much air is required for the complete com- 
bustion of one pound of coal ? 

Ans. By weight 12 pounds — by volume 150 cubic feet. 

197. What precaution is necessary regarding the tubes 
of a boiler in order to get the best results from the fuel ? 

Ans. The tubes should be kept clean and free from soot 
and scale. 

198. Should the steam jet cleaner be depended upon 
alone for cleaning the tubes? 

Ans. No. The scraper should also be used. 

199. How should safety valves be looked after? 

Ans. They should be ample in size, never overloaded, 
and should be tested at least once a day to see that they 
act freely. 



34 Steam Engineering 

206. At what point should the steam gauge pointer 
stand when the pressure is off? 
Arts. It -should stand at zero. 

201. What should be done in ease of low water in a 
boiler? 

A ns. The fire should be covered immediately with ashes, [] 
earth, or if neither is available use fresh coal. Draw the 
fire as soon as it can be done without increasing the heat. 

202. Should the rate of feeding the water be increased, 
in case of extremely low water in the boiler ? 

Ans. It should not, neither should the engine be stopped f. 
or the safety valve lifted, until the fires are out, and the 
boiler cooled down. 

203. In case of indications of cracks or blisters appear- 
ing on the boiler sheets, what should be done ? 

Ans. There should be no delay in making repairs. 

204. What should be done with fusible plugs when used ? 
Ans. They should be cleaned and carefully scraped on 

both water and fire sides at each washing out. 

205. How may the most economical results regarding | 
fuel be attained with a steam boiler ? 

Ans. By keeping the heating surfaces clean, both inside 
and outside, also careful firing, a little at a time, but keep- 
ing the grates covered. y 

206. Should cold water ever be fed into a boiler when 
it is under pressure? i 

Ans. Not when it can be avoided. 

207. How may foaming usually be stopped ? 

Ans. By checking the outflow of steam, by blowing 
down and pumping up, or bv checking the draft and fires. 

208. Should air be allowed to pass to the boiler or tubes, r 
except through the furnace? 



Care and Operation of Boilers 35 

Ans. It should not, as it will cause a waste of fuel. 

209. What should be done with leaks when discovered ? 
Ans. They should be repaired as soon as possible. 

210. What precautions should be observed when pre- 
paring to empty a boiler for washing out, or other pur- 
poses ? 

Ans. Allow it to cool down until there is no steam pres- 
sure, and until the brick work is cool also. 

211. When firing up a boiler what course should be 
pursued ? 

Ans. Steam should be raised very slowly, and rapid fir- 
ing avoided. 

212. What bad results follow too rapid firing up of a 
boiler ? 

Ans. Straining of the joints and seams caused by un- 
equal expansion. 

213. What should be done with a boiler that is to 
stand idle for any length of time? 

Ans. It should be emptied, and thoroughly dried. In 
case this is impracticable, fill it full of water, and put in 
a quantity of washing soda. 

214. How long a time may a boiler be safely operated 
between dates of washing out ? 

Ans. This depends upon the nature of the feed water. 
The time should never be longer than two weeks, and with 
very bad water, the boiler should be washed out once a 
week. 

215. Besides cleaning the boiler inside, what other very 
important work should the boiler washer perform while 
inside the boiler? 



36 Steam Engineering 

i 

Ans. He should closely examine all braces, stays, and 
rivets by tapping them with a hammer. Any loose or de- 
fective parts can usually be detected in this way. 

216. Describe four ways in which tube failures may 
occur. 

Ans. 1. Pitting. 2. Defective welds. 3. Bagging. 4. 
Scabbing and blistering. 

217. How may a great saving in fuel be effected with 
regard to the feed water ? 

Ans. By heating it with the exhaust steam from engines 
and pumps before passing it to the boilers. 

218. Describe the available heating surface of a station- 
ary boiler, of either type, return tubular or water tube. 

Ans. The lower half of the shell, and heads, and the 
combined cross sectional area of all the tubes. 

219. What should be the location of the water gauge 
glass, relative to the water level in the boiler? 

Ans. It should be located at such a height as to bring 
the lower end of the glass tube on a level with the danger 
point for low water in the boiler. 

220. Where should the lower gauge cock be located 
relative to the danger point ? 

Ans. About three inches above. 

222. Should an engineer or water tender depend entirely 
upon the water gauge glasses ? 

Ans. He should not, but should frequently open and try 
the gauge cocks. 

223. WTiat should be done with the entire water column 
several times a day? 

Ans. It should be blown out thoroughly. 

224. What should be done with the safety valves in 
order to make them reliable ? 



k 



Care and Operation of Boilers 37 

A ns. They should be allowed to blow off at least twice a 
week. 

225. Why is this necessary? 

Ans. Because the valves are liable to become corroded, 
and stick to their seats if not attended to properly. 

226. What is*the rule for finding the bursting pressure 
of boilers ? 

A ns. Multiply the tensile strength by the thickness and 
divide by one-half the diameter of the shell. 

227. How may the safe working pressure of a boiler be 
ascertained ? 

Ans. By dividing the bursting pressure by five, 

228. What is the rule for ascertaining the velocity of 
flow in a pump ? 

Ans. Multiply the number of strokes per minute by 
length of stroke in feet. This will give piston speed. 

229. How may velocity of flow in the discharge pipe of 
a pump be found ? 

Ans. Divide square of diameter of water piston by the 
square of the diameter of pipe, and multiply by piston speed 
per minute. 

230. What is the rule for finding velocity in feet per 
minute required to discharge a given quantity of water in 
a given time ? 

Ans. Multiply number of cubic feet to be discharged by 
144 and divide by area of pipe in inches. 

231. When the volume and velocity of water to be dis- 
charged are known, how may the area of the pipe be ascer- 
tained ? 

Ans. Multiply volume in cubic feet by 144 and divide 
by velocity in feet per minute. 



38 Steam Engineering 

232. What is one of the main requisites in the success- 
ful burning of coal in a boiler furnace ? 

Am. A good draft. 

233. What is a common cause of lost economy in the 
operation of boilers? 

Ans. Air leaks in the brick settings. 

234. Mention another source of loss in connection with 
mechanical stokers. 

Ans, The dead area of grate that is covered with a thin 
layer of clinker, and ash. 

235. What is meant by the expression "priming?" 
Ans. Carrying over into the cylinder of water in the 

form of fine spray mingled with the steam. 

236. How may this be prevented to a large extent? 
Ans. By placing a bafSe plate in the steam space of the 

boiler, directly under the dome. Steam separators may 
also be employed for this purpose. 

237. What should be the principal object in view in 
burning coal under a boiler? 

Ans. To transfer as many as possible of the total heat 
units in the coal, to the water in the boiler. 

237a. Describe the proper method of connecting a 
recently fired-up boiler with the steam main. 

Ans. Open the connecting valve slightly just 
enough to permit a small jet of steam to pass through 
which can be heard by placing the ear near the body 
of valve. Leave the valve in this position until the 
flow of steam stops. The valve may then be gradually 
opened until it is wide open. 



Combustion, Heat 



238. What is meant by the term combustion as used in 
steam engineering? 

Ans. It is the rapid chemical combination of oxygen 
with the carbon, hydrogen and sulphur in the fuel with 
the accompaniment of heat and light, 

239. What is meant by the symbol C0 2 ? 

Ans. C0 2 represents perfect combustion, viz., the cre- 
ation of carbon dioxide. 

240. What is the most abundant combustible in nature? 
Ans. Carbon. 

241. How many heat units are contained in one pound 
of pure carbon? 

Ans. 14,500. 

242. What is the heating value of one txrand of hydro- 
gen gas? 

Ans. 62,000. 

243. Give the composition of coal. 

Ans. Fixed carbon, volatile matter, ash and sulphur in 
various proportions, depending upon the quality of the 
coal. 

244. Is sulphur desirable as a constituent of coal? 

Ans. It is not. The gases formed from its combustion 
attack the metal of the boiler, causing corrosion. 

245. What office does nitrogen perform in combustion? 

39 



40 Steam Engineering 

Ans. No useful office. Kather it is a detriment, and 
in fact is the chief source of loss in furnaces. It is drawn 
in with the air. 

246. What is meant by the term calorific value of fuel ? 

Ans. The amount of heat liberated per pound of fuel 
undergoing perfect combustion. 

248. What are economizers in connection with a boiler 
plant? 

Ans. Coils or stacks of cast iron pipe placed within the 
smoke flue, or breeching and surrounded by the hot gases 
while the water is passed through the pipes on its way to 
the boilers, thus receiving an additional amount of heat. 

249. What two factors are necessary in order to attain 
economy in the burning of coal? 

Ans. A constant high furnace temperature and quick 
combustion. 

250. Define the term heat. 

Ans. Heat is the result of the vibration of the mole- 
cules or atoms composing matter. 

251. Upon what does the intensity of heat depend? 
Ans. Upon the rapidity of the agitation to which the 

molecules are subject. 

252. What are the general effects of heat? 

Ans. When heat is added to, or taken away from a 
body the temperature of the body is altered and its volume 
is varied. 

253. What is absolute zero? 

Ans. It is that degree of temperature at which, owing 
to the intense cold, a perfect gas would disappear. Abso- 
lute zero is 461° below the zero of the Fahrenheit ther- 
mometer. 



Combustion, Heat 41 

254. What is a heat unit (B. T. XL) ? 

Arts. It is the quantity of heat required to raise the tern* 
perature of one pound of water one degree, or from 39° 
to 40° F. 

255. What is the mechanical equivalent of heat? 
Arts. 778 foot pounds; in other words/ 778 pounds 

raised one foot high. 

256. What is the specific heat of any substance? 

Arts. The ratio of the quantity of heat required to raise 
a given weight of that substance one degree in tempera- 
ture, to the quantity of heat required to raise an equal 
weight of water one degree when the water is at its maxi- 
mum density, viz., 39.1° F. 

2'57. What is latent heat? 

Ans. Heat given to a body and not warming it. 

258. What is sensible heat? 

Ans. Heat given to a body and warming it. 

259. Of what is pure water composed? 

Ans. By volume — Hydrogen 2 parts, oxygen 1. 

By weight — Hydrogen 11.1 parte, oxygen 88.9. 

260. Is perfectly pure water desirable for use in a steam 
boiler ? 

Ans. It is not, as it will cause corrosion and pitting of 
the sheets. 

261. What two ingredients in water are the chief causes 
of incrustation in boilers ? 

Ans. The carbonates of lime and magnesia. 

262. What is steam? 

Ans. Steam is the vapor of water generated by an in- 
crease of the natural vibrations of molecules of the water 
through the application of heat. 



42 Steam Engineering 

263. What is saturated steam ? 

An-s. Steam taken directly from the boiler to the engine 
without being superheated. 

264. What is superheated steam? 

Arts. Sream that has been heated to a higher tempera- 
ture than that due to its pressure. 

265. What should be done with all pipes through which 
live steam is conducted for purposes of heating, or power? 

An& They should be well protected by a covering, in 
order to prevent loss of heat by radiation. 

6. In what respect should steam be cor 1 in its 

relation to the engir 

i*. Afl a " referring the heat energy from 

the boiler to the engine. 

266a. What is meant by the term "volume of 
steam"? 

Ans. The number of cubic feet in 1 pound weight 
■m 
■ob. What ifl meant by the expression "relative 
volume of steam ' ' ? 

Ans. The number of volumes un produced 

from one volume of wal ranee at 100 pounds 

gauge pressure the steam produced from 1 cu. ft. of 
water will occupy 237.6 cu. ft. of space. 



Evaporation Tests 



267. What is the primary object of an evaporation test ? 

Ans. To ascertain how many pounds of water the boilers 
are evaporating per pound of coal burned. 

268. What other important points relative to boiler 
operation may be determined by these tests? 

Ans. There are four. First — To determine the efficiency 
of the plant as an apparatus for the consumption of fuel, 
and the evaporation of water. Second — To determine the 
relative economy of different varieties of coal, and other 
fuels. Third — To determine whether or not the boilers 
are being operated as economically as they might be. 
Fourth — To determine whether the boilers are being over 
worked. 

269. In what condition should the testing apparatus 
be maintained? 

Ans. In first-class condition, ready to be used at any 
time for making a test. 

270. What should be done with the boiler, and all of 
its appurtenances preparatory to making a test? 

Ans. They should be put in good condition, by clean- 
ing, etc. 

271. How should the boiler under test be operated 
during the test? 

Ans. At its full capacity. 

272. Where should the water level be at the beginning, 
and close of the test? 

43 



44 Steam Engineering 

Ans. At the height ordinarily carried, and its position 
should be marked by tying a cord around one of the guard 
rods of the gauge glass. 
I 273. How long should the test last? 

Ans. About 10 hours. 

274. How is the percentage of moisture in the steam 
determined ? 

Ans. By means of the calorimeter. 

275. How many, and what kind of calorimeters are 
used for this purpose ? 

Ans. Two. The throttling calorimeter, and separating 
calorimeter. 

276. Upon what principle does the throttling calori- 
meter act? 

Ans. Upon the principle of temperatures. 

277. How does the separating calorimeter act ? 

Ans. It mechanically separates the water from a known 
volume of steam passing through it. 

278. In what other manner may the condition of steam 
regarding its dryness be approximated? 

Ans. By observing its appearance as it issues from a 
pet cock, or other small opening. 

279. How will steam containing 1 or 2 per cent of 
moisture appear under such conditions ? 

Ans. It will be transparent close to the orifice from 

which it issues. 

280. How is the chimney draft measured? 
Ans. By means of a draft gauge. 

281. What is the usual form of draft gauge? 
Ans. A glass tube bent in the shape of the letter U. 

282. Describe the action of a draft gauge. 



Evaporation Tests 45 

Arts. One leg of the U tube is connected to the chimney 
by a small rubber hose. The other leg is open to the at- 
mosphere. The tube is partly filled with water, which 
when there is no draft will stand at the same height in 
both legs. 

283. When there is a draft and the rubber hose is con- 
nected to the chimney how is the water in the U tube 
affected ? 

Ans. The draft suction causes the water in the leg to 
which the hose is connected, to rise while the level of the 
water in the other leg will be equally depressed. 

284. How is the intensity of the draft thus estimated ? 
Ans. In fractions of an inch, .5, .7 or .75 inches. 

285. What is the object of flue gas analysis? 

Ans. There are three. First — To determine the amount 
of excess air admitted to the furnace. Second — To de- 
termine the character of the combustion. Third — To as- 
certain the heat losses. 

286. What weight of oxygen is required for the com- 
plete combustion of one pound of carbon? 

Ans. 2.67 pounds. By volume, 32 cubic feet. 

287. What gaseous combination is produced by com- 
plete combustion? 

Ans. Carbon dioxide (C0 2 ). 

288. What is the result of imperfect combustion? 
Ans. Carbon monoxide (CO). 

289. How is the efficiency of the boiler and furnace 
ascertained through an evaporation test? 

Ans. By weighing the coal consumed and the water 
evaporated during a certain number of hours and dividing 
the number of pounds of water evaporated by the number 
of pounds of coal consumed. This will give number of 
pounds water evaporated per pound of coal. 



46 Steam Engineering 

290. What is meant by the term "equivalent evapora- 
tion r 

Ans. It assumes that the feed water enters the boiler 
at a temperature of 212°, and is evaporated into steam at 
212° and at atmospheric pressure. 

291. Why is this standard necessary in evaporation 
tests? 

Ans. Because of the variations in the temperature of 
the feed water used in different tests. 

292. What is meant by boiler horse-power? 

Ans. The evaporation of 3414 pounds water from a 
feed temperature of 212° into steam of the same tempera- 
ture; or the evaporation of 30 pounds water from a feed 
temperature of 100° into steam at 70 pounds gauge pres- 
sure. 

293. What is meant by the expression "total heat of 
evaporation ?" 

Ans. The sum of the sensible heat plus the latent heat, 
at boiling point. 

294. What is steam in its relation to the engine? 
Ans. It is merely a vehicle for transferring the heat 

energy from the boiler to the engine shaft. 



Steam Engines 



295. Into what two general classes are steam engines 
divided. 

Ans. Simple and compound. 

296. Describe a simple engine. 

Ans. A simple engine may be either condensing or non- 
condensing, but its leading characteristic is, that the steam 
is used in but one cylinder. 

297. What is a condensing engine? 

Ans. One in which the exhaust steam is passed into an 
air-tight vessel in which a vacuum is maintained, the ex- 
haust steam being there condensed by coming in contact 
with cold water, or a series of tubes through which cold 
water is being circulated. 

298. Describe a compound engine? 

Ans. A compound engine is one in which the steam is 
made to do work in two or more cylinders before it is al- 
lowed to exhaust. 

299. How is this accomplished? 

Ans. By causing the exhaust steam from the first, or 
high pressure cylinder, to pass into a second cylinder of 
larger diameter, and, if the engine be triple or quadruple 
expansion, from thence into a third or fourth cylinder, 
the diameters of which increase in regular ratio. 

300. What is a non-condensing engine ? 

Ans. One from which the steam exhausts directly into 
the atmosphere, or is used for heating purposes before 
passing out into the open air. 

47 



48 Steam Engineering 

301. What disadvantage does a non-condensing engine 
constantly labor under? 

Arts. The pressure of the atmosphere amounting to 
14.7 pounds per square inch is constantly in resistance to 
the motion of the piston. 

302. Mention several other causes that tend to increase 
the back pressure upon the piston of a non-condensing en- 
gine. 

Ans. The resistance of bends and turns in the exhaust 
pipe, also causing the exhaust to pass through feed water 
heaters or heating coils. 

304. What is back pressure? 

Ans. Pressure that tends to retard the forward stroke 
of the piston. 

305. What advantage has a condensing engine over a 
non-condensing engine? 

Ans. The atmospheric pressure is removed from in front 
of the piston to a degree corresponding to the height of 
the vacuum that is maintained in the condenser. 

306. How many classes of condensers are there in gen- 
eral use? 

Ans. Two; jet condensers and surface condensers. 

307. Describe a Jet condenser. 

Ans. One in which the steam is exhausted into an air- 
tight vessel, and is there condensed by coming in contact 
with a jet or spray of cold water. 

308. How is this water removed? 

Ans. By means of the air pump, which also maintains 
a vacuum in the condenser. 

309. Describe a surface condenser. 



Steam Engines 49 

Ans. It is an air-tight vessel, either cylindrical or 
rectangular in shape, fitted with a large number of brass 
or copper tubes, of small diameter, through which the cold 
water is forced by the circulating pump. A vacuum is 
maintained in the body of the condenser by the air pump, 
and the steam exhausted into this is condensed by coming 
in contact with the cool surface of the tubes. In some 
cases the steam passes through the tubes in place of around 
them, the condensing water being forced into and through 
the body of the condenser, and the vacuum being main- 
tained in the tubes. 

310. Describe an injector condenser. 

Ans. A condenser in which the cold water is forced 
through an annular enlargement of the exhaust pipe, and 
passing down into a nozzle which gradually contracts. The 
exhaust steam entering at the same time is condensed, the 
water rushing through the nozzle with a velocity sufficient 
to create a vacuum. 

311. About what quantity of water is required per 
horse-power per hour to condense the exhaust steam from 
an engine? 

Ans. About 38 to 40 gallons, depending upon the tem- 
perature of the condensing water. 

312. What three factors are necessary to insure good 
economy with multiple cylinder compound engines ? 

Ans. First — A high initial pressure. Second — Expan- 
sion of the steam to greatest extent possible. Third — Pro- 
tecting the surfaces of the cylinders from cooling influences. 

313. Describe a cross compound engine. 

Ans. An engine consisting of two cylinders, each hav- 
ing its own connecting rod and crank, the cranks being 
set at opposite ends of the engine shaft, and at an angle 



SO Steam Engineering 

of 90° to each other. The high pressure cylinder exhausts 
into the low pressure cylinder, usually through a receiver. 

314, Describe a tandem compound engine. 

Ans. An engine having the two cylinders arranged tan- 
dem to each other, with a common piston rod, and connect- 
ing rod. 

315. What advantage is gained by this design? 

Ans. A much shorter and more direct route for the 
exhaust steam in its passage from the high to the low pres- 
sure cylinder. 

315a. What type of condenser is the most reliable 
and economical for general purposes? 

Ans. The jet condenser with air pump attached. 

315b. Give a reason for this. 

Ans. The supply of condensing water may be 
drawn from a well or other source lower than the level 
of the condenser. 

315c. What is a force injection and for what is it 
used? 

Ans. A connection between the condenser and 
water main or tank for the purpose of admitting cold 
water into the condenser when starting the engine. 



Valves and Valve Setting 

316. What inportant features in the operation of an 
engine are dependent upon a correct adjustment of the 
valves ? 

Arts. The efficiency of the engine, the economical use 
of steam, and the regular and quiet action of the engine. 

317. How many different types of valves are there in 
general use? 

Ans. Slide, poppet, rotative, piston, gridiron, etc. 

318. What are the basic principles governing the ad- 
justment of the valves of an engine, regardless of the type? 

Ans. Admission, cut-off, release, and exhaust closure; 
each of these functions to occur at the proper moment dar- 
ing one stroke of the piston. 

319. Name two important functions of a valve. 
Ans. Lap and lead. 

320. What is the effect of increasing outside lap? 
Ans. Later admission, and an earlier cut off. 

321. What results from increasing inside lap? 

Ans. Earlier exhaust closure, and an increased conpres- 
sion. 

322. What advantage has an engine of the four yalve 
type over a single valve engine? 

Ans. Each individual valve may be adjusted in- 
pendently of the others. 

323. If a valve had neither lap nor lead what wixAd 
be the position of the eccentric relative to the crank ? 

51 



52 Steam Engineering 

Ans. 90° ahead of the crank. 

324. What is meant by the term "angular advance/' and 
why is it necessary ? 

Ans. The distance that the high point of the eccentric 
is set ahead of a line at right angles with the crank. It is 
necessary in order to give the valve lap, and lead. 

325. What is the first function of the valve at the com- 
mencement of the stroke ? 

Ans. Lead, or admission. 

326. What is the second function? 
Ans. Full port opening. 

327. What is the travel of a valve equal to? 

Ans. Twice the port opening plus twice the outside lap. 

328. What is the third function of the valve? 
Ans. Cut off. 

329. What is the fourth function? 
Ans. Exhaust closure, or compression. 

330. What will be the effect if the valve has no inside 
lap? 

Ans. An early release, and no compression. 

331. What is meant by "radius of eccentricity ?" 
Ans. One half the travel of the valve. 

332. What is an eccentric? 

Ans. A mechanical device for converting rotary into 
reciprocating motion. Its center of revolution is apart 
from its center of formation. 

333. What is the "throw" of an eccentric? 

Ans. The distance from the center of the eccentric to 
the center of the shaft. 

334. What is meant by eccentric position ? 



\ dives and Valve Setting 53 

A ns. The location of the highest point of the eccentric 
relative to the center of the crank pin, expressed in degrees. 

335. What is valve travel? 

Ans. The distance covered by the valve in its move- 
ment. 

336. What is lap? 
Ans. The amount that the ends of the valve project 

over the edges of the ports when the valve is at mid travel. 

337. What is inside lap? 
Ans. The lap of the inside, or exhaust edge of the valve 

over the inside edge of the port. 

338. What is outside lap ? 
Ans. The lap of the outside edge of the valve over the 

outside edge of the port. 

339. What is lead? 
Ans. The amount that the port is open when the crank 

is on the dead center. 

340. Why must a valve have outside lap? 
Ans. Because admission and cut off are controlled 

thereby. 

341. Why should a valve have inside lap ? 
Ans. In order that release and compression may be 

properly controlled. 

342. What is the effect of decreasing the angular ad- 
vance? 

Ans. All the important functions of the valve occur 
later. 

343. What results follow from decreasing the travel of 
the valve? 

Ans. Less lead, a later admission and release, and an 
earlier cut off and compression. 

344. What is meant by automatic or variable cut off? 



54 Steam Engineering 

Ans. A system in which full boiler pressure is constantly 
maintained in the valve chest, the speed being regulated by 
the governor controlling the point of cut off. 

345. What is meant by fixed cut off? 

Ans. When the point of cut off remains the same, re- 
gardless of the load, the speed being regulated by throttling 
the steam. 

346. What three changes must be made in order to 
cause an earlier cut off on an engine that has a fixed cut off ? 

Ans. First — Increase the angular advance. Second — 
Increase the outside lap. Third — Increase the inside lap. 

347. What is the first step in valve setting? 
Am*. To place the engine on the dead center. 

348. What is meant by the dead center? 

Ans. When the piston is at the end of the stroke, and 
the centers of the crank shaft, crank pin, and cross head 
pin are in line. 

349. What rule should be observed in turning an en- 
gine to place it on the dead center? 

Ans. Always turn it in the direction in which it is to 
run. 

350. Why is this necessary? 

Ans. In order to guard against errors which might 
result from lost motion in the parts. 

351. Having placed the engine on the dead center, what 
is to be done next? 

Ans, Adjust the eccentric rod to the proper length? 

352. What should be done with the valve before con- 
necting it with the eccentric rod? 

Ans, It should be placed at mid travel, and marked. 



Valves and Valve Setting 55 

353. What is necessary before the valve can be placed 
in its central position? 

Ans. The exact amount of outside lap must be known. 

354. What amount of lead is usually given to the Talve ? 
Ans. From £$ in. to % in. depending upon the size of 

the engine. 

355. What is the function of the governor? 
Ans. To properly regulate the speed of the engine. 

356. Explain the action of a governor? 

Ans. Its action is based upon the principle of the cen- 
trifugal, and centripetal forces, which cause the balls or 
weights attached to the arms, to fly outward or inward as 
their speed of revolution increases or decreases. 

.357. In what manner is this movement of the balls 
caused to regulate the speed? 

Ans. In the pendulum or fly ball governor, the motion 
is transferred by means of levers and rods to the cut oil 
mechanism. In the shaft governor the changes in the 
position of the weights change the angular advance of the 
eccentric, thus causing an earlier or later cut off, according 
as the load is light, or heavy. 

358. In what way does the throttling governor regulate 
the speed of an engine? 

Ans. It controls the position of a valve in the steam 
pipe, opening or closing it according as the engine needs 
more, or lees steam to maintain a regular speed. 

359. What is compression? 

Ans. If the exhaust port is closed by the valve, just be- 
fore the piston reaches the end of stroke, a portion of the 
steam will be entrapped in the cylinder, and being ahead 
of the piston will be compressed. 

360. Is there any advantage in this? 



56 Steam Engineering 

Ans. Yes. The steam thus compressed acts as a cush- 
ion for the piston, preventing shock or jar to the moving 
parts on reaching the end of the stroke. 

361. What is an adjustable cut off? 

Ans. One in which the point of cut off may be adjusted 
by a hand wheel attached to the valve stem of a throttling 
governor. 

361a. "What precautions should be taken regarding 
the operation of the fly-ball or throttling type of 
governor? 

Ans. The small valve stem should not be packed 
too tight. The packing nut should be left loose enough 
to allow a slight leakage of steam past the stem. This 
will permit the governor to work freely and the speed 
of the engine will be regular. 

361b. Describe the action of an automatic or vari- 
able cut-off engine. 

Ans. The full boiler pressure is constantly in the 
valve chest and the speed of the engine is regulated by 
the governor controlling the point of cut-off causing it 
to occur earlier or later according as the load on the 
engine is lighter or heavier. 



Definitions 



362. What is absolute pressure? 

Arts. Pressure reckoned from a perfect vacuum. 

363. What is gauge pressure? 

Ans. Pressure above atmospheric pressure. 

364. What is initial pressure? 

Ans. Pressure in the cylinder at the beginning of the 
stroke. 

365. What is terminal pressure? 

( Ans. Pressure in the cylinder at the end of the stroke. 

366. What is mean effective pressure (M. B. P.) ? 
Ans. The average pressure acting upon the pistoa 

throughout the stroke. 

367. What is back pressure? 

Ans. Pressure tending to retard the forward stroke of 
the piston. 

368. What is absolute back pressure? 

Ans. Back pressure measured from a perfect vacuum. 

369. What is the ratio of expansion? 

Ans. The relative volume of steam in the cylinder at 
point of release, compared to volume at cut off. 

370. What is wire drawing of steam? 

Ans. Eestricted passage of tire steam caused by too 
small a steam pipe. 

371. What is condenser pressure? 

Ans. Pressure existing in the condenser caused by tlra 
lack of vacuum. 

57 



A 



58 Steam Engineering 

372. What is vacuum? 

Am. That condition existing within a closed vessel from 
which all matter, including air has been expelled. 

373. What is absolute zero? 
Am. 461.2 ° below zero Pahr. 

374. What is piston displacement? 

Ans. The space swept through by the piston in a single 
stroke. 

375. What is piston clearance? 

Ans. The distance between the piston and cylinder head 
at the end of the stroke. 

376. What is steam clearance ? 

Ans. The distance between the piston at end of stroke, 
and the valve face. 

377. What is a horse power (H. P.) ? 

Ans. 33,000 lbs. raised one foot in one minute of time, 

378. What is indicated horse power (I. H. P.) ? 

Ans. The horse power as shown by the indicator dia- 
gram. 

379. What is piston speed? 

Ans. The distance in feet traveled by the piston in one 
minute. 

380. Give the rule for figuring the horse power ? 

Ans. Area of piston in square inches XM. E. P. X piston 
speed-^33,000. 

381. What is net horse power? 
Ans. I. H. P. minus engine friction. 

382. Define Boyle's law of expanding gasee? 

Ans. Pressure at constant temperature varies inversely 
ae the space it occupies. 

383. What is an adiabatie curve? 



( 



Definitions 89 

Ans. The curve of expanding gas that loses no heat 
while expanding. 

384. What is an isothermal curve ? 
Ans. The curve of an expanding gas of constant tem- 
perature, but influenced by moisture. 

385. What is an expansion curve? 
Ans. The curve traced upon the diagram by the indi- 
cator pencil. 

386. Define the first law of thermodynamics. 
Ans. Heat and mechanical energy are mutually con- 
vertible. 

387. What is power? 
Ans. The rate of doing work. 

388. What is the unit of work? 
Ans. The foot pound, viz., the raising of one pomid, 

one foot high. 

389. Define the first law of motion? 
Ans. All bodies continue either in a state of rest, or of 

uniform motion in a straight line, unless compelled bf im- 
pressed forces to change that state. 

390. What is work, mechanically considered? 
Ans. Pressure X distance passed through X time. 

391. What is momentum? 
A ns. Mass X density. 

392. What is dynamics? 
Ans. The science of moving powers. 

393. What is force? 
Ans. That which alters the motion of a body, or pats 

in motion a body that was at rest. 

394. Define the maximum theoretical duty of steam? 
Ans. Mechanical equivalent of heat X total heat unite 

in a pound of steam? 



A 



60 Steam Engineering 

395. How may steam efficiency be expressed? 

Ans. Heat converted into useful work-^-heat expended. 

396. How may engine efficiency be expressed ? 

Ans. Heat converted into useful work -r- total heat re- 
ceived in the steam. 

397. How may efficiency of the plant be expressed ? 
Ans. Heat converted into useful work-^-calorifie or heat 

value of the fuel. 

398. What is horse power constant ? 

Ans. The power the engine would develop with one 
pound M. E. P. 

399. What is meant by steam consumption per H. P. 
per hour? 

Ans. Weight in pounds of steam used-^-H. P. developed. 

400. What are ordinates as applied to indicator dia- 
grams ? 

Ans. Parallel lines drawn at equal distances across the 
face of the diagram, perpendicular to atmospheric line. 

400a. Define the meaning of logarithms. 

Ans. A series of numbers having a certain relation 
to the series of natural numbers by means of which 
many arithmetical problems are made comparatively 
easy to solve. 

4O0b. How is the hyperbolic logarithm found ? 

Ans. Multiply the common logarithm by the con- 
stant 2.3. 



Indicator 



401. What two important points are gained by the use 
of the indicator? 

Arts, First — It shows the average pressure upon the 
piston throughout the stroke. Second — It shows the action 
of the valve or valves in admission, cut off and release of 
the steam. 

402. What is the first principle of the indicator? 

Arts. Pressure of the steam in the engine cylinder dur- 
ing an entire revolution, against a small piston in the cylin- 
der of the indicator. 

403. What resistance is in front of the indicator piston? 
Ans. A spiral spring of known tension. 

404. What is the second principle of the indicator ? 

Ans. By means of a multiplying mechanism of levers, 
the stroke of the indicator piston is communicated to a 
pencil moving in a straight line. 

405. What is the third principle of the indicator? 

Ans. By means of a reducing mechanism and cord, the 
motion of the engine piston during an entire revolution is 
imparted to a small rotating drum, to which is attached a 
piece of blank paper. 

406. How is a diagram obtained ? 

Ans. The pencil is held against the paper and thus trace*? 
a diagram of the action of the steam within the engine 
cylinder. 

407. What is the atmospheric line? 

61 



62 Steam Engineering 

Ans. A line drawn by the indicator pencil before com- 
munication is established between engine cylinder and indi- 
cator cylinder. 

408. Where should a diagram from a non-condensing 
engine appear relative to the atmospheric line? 

Am. It should appear above the atmospheric line. 

409. Where should the diagram from a condensing en- 
gine appear? 

Ans. Partly above, and partly below the atmospheric 
line. 

410. What is the best reducing motion to use? 
Ans. The reducing wheel. 

411. How is the indicator attached to the engine cylin- 
der? 

Ans. By means of half -inch pipe tapped into the side of 
the cylinder near the ends. 

412. How are the springs numbered? 

Ans. They are made for various pressures, and num- 
bered accordingly. 

413. What is a good rule to follow in selecting a spring? 
Ans. Select one numbered one-half as high as the boiler 

pressure, which will give a diagram about two inches high. 

414. What data should be noted upon the diagrams 
when they are taken? 

Ans. Boiler pressure ; time when taken, and which end 
of cylinder, head, or crank. 

415. What pressure must always be deducted from the 
mean forward pressure (M. F. P.) in calculations for 
power? 

Am. The back pressure. 

416. What bad effects follow unequal cut off? 



Indicator 63 

Ans. The engine will not develop the power that it is 
capable of — uneven strains will be set up. 

417. What is a convenient size for a diagram? 
Ans. li/2 or 2 inches high, and 2 or 2y 2 inches long. 

418. What precaution regarding the pipe connections 
of the indicator should always be observed before taking 
diagrams ? 

Ans. They should be thoroughly blown out, and cleaned 
of all dirt. 

419. How is the ratio of expansion found? 

Ans. Divide absolute initial pressure by absolute ter- 
minal pressure. 

420. Name a very important factor in the calculation 
of steam consumption of an engine. 

Ans. The clearance space. 

4:21. What is one of the first requisites in power calcu- 
lations ? 

Ans. To ascertain the M. E. P. 

422. How is this done? 

Ans. In several ways, for instance by means of ordinates, 
or it may be obtained by the use of the Planimeter. 

422a. What is a Planimeter? 

Avis. An instrument which will accurately measure 
in sq. friches, the area of any plain surface, no matter 
how irregular the outline or boundary line may be. 

422b. For what purpose is the planimeter particu- 
larly well adapted? 

Ans. For measuring the areas of indicator dia- 
grams, It shows at once the area of the diagram in 
square inches and decimal fractions of a square inch. 



64 Steam Engineering 

422c. What does the area of an indicator diagram 
represent ? 

Ans. The actual work done by the steam acting 
upon or against the piston. 

422d. What is the first requisite in making power 
calculations from indicator diagrams? 

Ans. To obtain the average height or width of the 
diagram assuming it were reduced to a plain paral- 
lelogram. 

422e. Having ascertained the area of a diagram in 
square inches, how may the average height be found? 

Ans. Divide the area in square inches by the length 
of the diagram in inches. 

422f. How is the M. E. P. as shown by the diagram 
obtained? 

Ans. Multiply the average height by the scale. 

422g. Give a still more simple method for finding the 
M. E. P. 

Ans. Multiply area of diagram in square inches by 
the scale and divide by the length of the diagram in 
inches. 



- 



Lubrication 



423. What is one of the most important problems eon- 
nected with engine operation ? 

Arts. The proper lubrication of the bearings. 

424. What is friction? 

Ans. The resistance caused by the motion of a body m 
contact with another body that does not partake of its 
motion. 

425. What is the first law of friction? 

Ans. Friction varies in proportion to the pressure cm 
the surfaces in contact. 

426. Define the second law of friction. 

Ans. Friction is independent of the areas of surface in 
contact. 

427. What is the third law of friction? 

Ans. Friction increases with the roughness of the sur* 
faces, and decreases as the surfaces become smoother. 

428. What is the fourth law of friction ? 

Ans. Friction is greatest at the beginning of motion. 

429. Give the fifth law of friction? 

Ans. Friction is greater between soft bodies than it is 
between hard bodies. 

430. When, and by whom were these laws first formu- 
lated? 

Ans. In 1831-33 by Gen. Arthur Morin, a French en- 
gineer. 

431. What is the tendency of friction with machinery 
in operation? 

65 



$6 Steam Engineering 

Ans. It tends to cause the parts to adhere to each othefc 

432. How may this friction- be largely obviated ? 
Ans. By proper lubrication of the rubbing surfaces. 

433. Does friction serve any good purpose ? 

Ans. Yes, for instance the friction of the belt in con- 
tact with the rim of the pulley, also the friction of the 
driving wheels of a locomotive. 

434. How many kinds of friction are there in connec- 
tion with machinery in operation ? 

Ans. Two, viz., the friction of solids, and the friction 
of liqni 

435. What is meant by the term co-efficient of friction? 
Ans. The ratio of the power required to move a body, 

and the pressure on that body. 

436. What should be the object sought in the design 
of engine bearings? 

Ans. To obtain as large a rubbing surface as possible. 

43?. Mention some of the qualities that a good lubri- 
cating oil should possess. 

Ans. It should have a good "body? — must not dry or 
"gum ;" must not be easily thinned by heat, or thickened by 
cold. Must be free from all gritty substances. 

438. What is the proper kind of oil to use on a bearing 
that has -tarted to heat? 

Ans. Cylinder oil, owing to its high fire test. 

439. Is graphite, or plumbago a good lubricant? 
Ans. It is in many cases. 

440. What is the essential function of graphite ? 
Ans. It is an auxiliary, or accessory lubricant. 

441. Mention some of the points that govern interior 
lubrication of engine parts. 



• 



Lubrication 67 

Arts. The conditions of the surfaces ; the steam pressure ; 
the amount of moisture in the steam ; piston speed ; weight, 
and fit of moving parts, etc. 

442. What properties should a good cylinder oil possess ? 
Arts. It must be of high flash test; must have good 

viscosity, or body when in contact with hot surfaces. 

443. Upon what does the successful lubrication of an 
engine largely depend? 

Arts. Upon the character of the lubricating appliances 
used. 

444. What system of lubrication for cylinders, and 
valves is most largely used ? 

Arts. The hydrostatic, or sight-feed type of lubricator. 

445. What other system has come into extensive use is 
late years? 

Ans. The force feed, or mechanically operated oil pump, 

445a. Mention some of the advantages gained by 
the use of the force feed oil pump. 

Ans. It is positive in action and may always be 
depended upon. It is not wasteful of oil for the reason 
that its action is governed by the speed of the engine, 

445b. How is the force feed oil pump operated? 

Ans. The connecting rod of the pump is attached 
to any movable part of the engine that will give it 
a reciprocating motion. 

445c. Describe a mechanical lubricator that will 
feed graphite along with the oil. 

Ans. Inside the oil reservoir there is located a spiral 
agitating device which revolves, thus keeping the oil 
and graphite thoroughly mixed. 

445d. From whence does this mixing device receive 
its motion? 



68 Steam Engineering 

445d. From whence does this mixing device receive 
its motion? 

Ans. From a set of bevel gears driven by a belt on 
the wheel of the pump. 

445e. In what proportions are the oil and graphite 
usually mixed when filling oil reservoir? 

Ans. Two or three teaspoonsful of graphite to a 
pint of oil. Another rule might be three teaspoonsful 
of graphite per day for a 150 horse power engine. 



The Steam Turbine 

446. Explain the chief points of difference between 
the action of the reciprocating steam engine, and the steam 

turbine. 

Ans. The piston of the reciprocating engine is driven 
back and forth by the static expansive force of the steam ; 
while in the steam turbine, not only is this static expansive 
force made to do work, but the velocity of the steam in ex- 
panding from a high, to a low pressure is also utilized in 
turning the rotor of the turbine. 

447. What other important factors enter into the opera- 
tion of a steam turbine? 

Arts. The principles of reaction and impulse. 

448. Name several of the more important advantages 
that the turbine has over the reciprocating engine. 

Ans. First, highly superheated steam of a high initial 
pressure may be used in the turbine. Second, a larger 
proportion of the heat in the steam may be converted into 
work with the turbine. Third, there is much less friction 
with the turbine. 

449. What is the most economical method of disposing 
of the exhaust steam from a turbine? 

Ans. By allowing it to pass into a condenser. 

450. Will the turbine expand the steam to as low a 
pressure as the reciprocating engine will? 

Ans. Yes, and even lower. 

69 



70 Steam Engineering 

451. What type of condensing apparatus is necessary 
with the steam turbine. 

Ans. The same kind that is used on reciprocating en- 
gines. 

452. How low will a well regulated turbine allow the 
steam to expand ? 

Ans. To within one inch of the vacuum existing in 
the condenser. 

453. What is the theoretical velocity of steam under 
100 lbs. pressure if allowed to discharge into a vacuum of 
28 inches? 

Ans. 3860 feet per second. 

454. How many ft. lbs. of energy would one cubic ft. 
of steam thus exert? 

Ans. 59,900 ft. lbs. 

455. What is the ratio of bucket speed to jet speed for 
impulse wheels. 

Ans. Bucket speed equals one-half of jet speed. 

456. What should be the ratio between bucket speed 
and jet speed, for reaction wheels. 

Ans. 1 to 1. That is, the two speeds should be equal. 

457. What should be the form or curvature of the 
blades, or buckets? 

Ans. They should be of such form as will permit expan- 
sion of the steam with the least amount of friction, or eddy 
currents. 

458. How are the stuffing boxes of steam turbines usu- 
ally kept cooled? 

Ans. By means of water applied in various ways. 

459. How is the speed of steam turbines usually regu- 
lated? 



Steam Turbines 71 

Ans. By simple throttling. 

460. What are the ideal conditions under which a tur- 
bine should work ? 

Ans. A full initial pressure, and all cross sections of 
steam passages to be suitable to the power required. 

461. Of what type is the Westinghouse-Parsons turbine ? 
Ans. It is both an impulse and reaction turbine. 

462. How are the clearances between the blades pre- 
served in this turbine? 

Ans. By means of balancing pistons on the shaft. 

463. What is the usual velocity of the steam in the 
Westinghouse-Parsons turbine ? 

Ans. 600 ft. per second. 

464. How does the efficiency of steam turbines compare 
with that of reciprocating engines? 

Ans. It is generally higher. 

465. How is the heat energy in the steam imparted to 
the wheels of the Curtis turbine? 

Ans. Both by impulse and reaction. 

466. Describe the method of admission in the Curtis 
turbine. 

Ans. The steam is admitted through expanding nozzles 
in which nearly all of the expansive force of the steam is 
transformed into the force of velocity. The steam is caused 
to pass through one, two, or more stages of moving ele- 
ments, each stage having its own set of expanding nozzles, 
each succeeding set of nozzles being greater in number and 
of larger area than the preceding set. 

467. What is the ratio of expansion in these nozzles? 



72 Steam Engineering 

Ans. The ratio of expansion within these nozzles de- 
pends upon the number of stages, as, for instance, in a two- 
stage machine, the steam enters the initial set of nozzles at 
boiler pressure, say 180 lbs. It leaves these nozzles and 
enters the first set of moving blades at a pressure of about 
15 lbs. 

468. In a four-stage machine, with 180 lbs initial pres- 
sure, what would be the pressures at the different stages ? 

Ans, First stage, 50 lbs.; second stage, 5 lbs.; third 
stage, partial vacuum, and fourth stage, condenser vacuum. 

469. How are the revolving parts of the Curtis turbine 
supported ? 

Ans. Upon a vertical shaft, which in turn is supported 
by, and runs upon a step bearing at the bottom. 

470. How is this step bearing lubricated? 

Ans. Oil is forced under pressure by a steam or elec- 
trically driven pump, the oil passing up from beneath. 

471. How is the speed of the Curtis turbine regulated? 
Ans. By varying the number of nozzles in flow. 

472. How are the clearances adjusted in the Curtis 
turbine? 

Ans. By means of the large step screw at the bottom. 

473. How is the shaft packed to prevent steam leakage ? 
Ans. With carbon blocks made into rings fitting the 

shaft. 

474. What type of turbine is the De Laval ? 
Ans. It is purely an impulse wheel. 

475. What is the speed of the wheel ? 

Ans. From 10,000 to 30,000 revolutions per minute. 

476. How is the heat energy in the steam utilized in 
the De Laval turbine? 

Ans. In the production of velocity. 



Steam Turbines 73 

477. What is the velocity of the steam as it issues from 
the expanding nozzles and impinges against the buckets? 

Am. About 4,000 ft. per second. 

478. What is the usual peripheral speed of the wheel ? 
Ans. 1,200 to 1,300 feet per second. 

479. Of what type is the Allis-Chalmers steam turbine ? 
Ans. It is essentially of the Parsons type. 

480. How are the clearances between the revolving and 
stationary blades preserved? 

Ans. By a thrust bearing. 

481. What kind of bearings has the Allis-Chalmers 
turbine ? 

Ans. Self-adjusting ball and socket bearings. 

482. What is the first move in preparing to start a 
steam turbine? 

Ans. Open the throttle slightly and allow a small vol- 
ume of steam to flow through in order to warm the tur- 
bine. 

483. What should be done next? 
Ans. Start the auxiliary oil pump. 

484. What are the principal precautions to be observed 
when starting a steam turbine? 

Ans. To see that the turbine is properly warmed, also 
to be certain that the oil is circulating freely through the 
bearings. 

485. What type of turbine is the Hamilton-Holzwarih 
steam turbine? 

Ans. It is an impulse turbine. 

480. Describe in brief its construction? 

Ans. There are no balancing pistons in this machine, 
the axial thrust of the shaft being taken up by a throat 
ball-bearing. The interior of the cylinder is divided into 



74 Steam Engineering 

a series of stages by stationary disc are set in 

grooves in the cylinder and are bored in the center to allow 
the shaft, or rather the hubs of the running wheels that are 
keyed to the shaft, to revolve in ore. 

437. In what respect does this turbine resemble a com- 

:nd reciprocating engine? 

Ans. The steam is first admitted to the high pressure 
rasing, and from there it p. low pressure cas- 

ing, which is larger in diameter. 

488. Describe the action of the steam upon the blades? 

Ans. The expansion of the steam takes place entirely 
within the stationary blades, which also change the direc- 
tion of its flow, distributing it to the running vane>. 

439. What additional function do the stationary vanes 
perform ? 

Ans. They take the back pressure, thus acting as balanc- 
ing pistons. 

490. Wl e of governor has this turbine? 
Ans. The spring and weight type. 

491. How are the bearings lubricate 

Ans. The oil is forced into the bearing* pressure 

an oil pump. 

492. Of what type is the Bateau steam tr 

Ans. It is an impulse turbine having wheels of thin 
plates, slightly conical. 

493. How is the rotor balanced? 

Ans. The same pressure exists on both sides of each 
rotating wheel. 

494. 1 he steam act by velocity or pressure? 
Ans. By velocity in this case. 

495. What are the essential features of the Eeidler- 
Btui rbine? 



Steam Turbines 75 

Ans. The peculiar form of bucket, and the parallel 
return of the steam. 

496. What is meant by parallel return of the steam? 
Ans. The steam enters the buckets through nozzles, 

and is deflected through an angle of 180 degrees, thus leav- 
ing the rotating buckets in a direction parallel to that of 
its entrance. 

497. Describe the action of the steam within the Beid- 
ler-Stumpf turbine. 

Ans. Instead of escaping after having once passed 
through the buckets, it is caught by the guides or stationary 
buckets and returned to the wheel; this process being re- 
peated again, and again until all of the energy in the steam 
has been made to do work. 

498. How many types of this turbine are there ? 

Ans. Two, viz. : The single flow, and the double flow. 

499. How is the highest efficiency obtained in the oper- 
ation of the steam turbine ? 

Ans. By allowing the exhaust steam to pass into a 
condenser. 

500. Is it possible to maintain as high vacuum with 
the turbine as with a reciprocating engine? 

Ans. Experience demonstrates that a higher vacuum 
may be maintained in the condenser of a turbine than is 
possible with reciprocating engines. 

501. What kind of condensing apparatus may be used 
with steam turbines? 

Ans. Any one of the modern improved types. 

502. What is required in order to maintain a high 
vacuum in any type of condenser ? 

Ans. That all entrained air be excluded. 

503. How may this be accomplished ? 



76 Steam Engineering 

Ans. By means of a dry air pump. 

504. In what manner does the dry air pump differ from 
an ordinary air pump ? 

Ans. The dry air pump handles no water, and the clear- 
ances are made as small as possible. 

505. To what extent does the steam turbine expand its 
working steam? 

Ans. To within one inch of the vacuum existing within 
the condenser. 

506. Is the steam turbine adapted to the use of super- 
heated steam? 

Ans. It is. Highly superheated steam may be used, and 
a high vacuum maintained. 

507. Is the water of condensation from turbines desir- 
able for boiler feed ? 

Ans. It is, for the reason that it contains no lubricating 
oil, and is a comparatively pure water. 



^ 



The Gas Engine 



508. In what respect does the gas engine differ from the 
steam engine structurally? 

Ans. It is a much more ponderous machine than a steam 
engine of equal output, and usually requires a much heavier 
crank shaft. 

509. Why should this be? 

Ans. Because the ordinary four-stroke-cycle, gas engine 
has only one working stroke in four, and requires four 
times as much cylinder area for a given amount of work, 
as would a steam engine for the same work. 

510. Define the difference between a single acting four 
stroke cycle and a double acting or two stroke cycle gas 
engine in their operation. 

Ans. In the four stroke engine two revolutions of the 
crank are required for one cycle. In the double acting or 
two stroke, the cycle is completed in one revolution of the 
crank. 

511. Why are gas engine crank shafts made larger in 
proportion than those of steam engines? 

Ans. In order that they may withstand the increased 
torsional strains. 

512. What causes the pressure behind the piston of the 
gas engine? 

Ans. The combustion within the cylinder of a charge 
of gas and air properly mbted to form an explosive, and 
admitted at the proper moment. 

513. When is this proper moment? 

77 



78 Steam Engineering 

Ans. When the piston is at the end of its instroke 
ready to start outward. 

514. Define the stages of a four cycle engine. 

Ans. First, induction; during an out stroke of the 
piston, air and gas are drawn into the cylinder in the 
proper proportions. Second, compression: on the return 
stroke the piston compresses this combustible mixture 
into the clearance space. Third, explosion ; ignition of the 
compressed charge causes a rapid rise of pressure and sub- 
sequent expansion of products. Fourth, expulsion; the 
expanded gases are expelled by the returning piston. 

515. Define the stages of a two cycle gas engine. 

Ans. First, compression of the charge. Second, igni- 
tion, explosion, and expansion, and at the end of the 
stroke the expanded products are expelled, and the cylinder 
filled by another charge of air and gas under pressure. 

516. How many compression chambers are needed for 
the two cycle gas engine? 

Ans. Two; for the reason that this type of gas engine 
requires two cylinders, either side by side, or tandem, and 
the charge of gas and air is being received in one cylinder, 
while the previous charge in the other cylinder is being 
compressed preparatory for explosion. 

517. How is the usefulness of the gas engine as a prime 
mover made apparent? 

Ans. By the fact that a suitable power gas may now be 
produced from almost any kind of commercial fuel. 

518. What are the relative volumes of gas and air re- 
quired for combustion in a gas engine ? 

Ans. This depends upon the kind of gas. Xatural gas 
requires 10 to 12 eu. ft. of air per cubic foot of gas, while 
producer gas requires equal volumes of gas and air. 



The Gas Engine 79 

519. Is blast furnace gas suitable for fuel gas? 

Ans. Yes, because it is slow burning, thus permitting 
high compression. 

520. To what pressures may it be compressed ? 
Ans. 160 to 200 lbs. per sq. in. 

521. Is the^e as much heat in a given volume of blast 
furnace gas as in the same volume of natural gas ? 

Ans. No,- there is about 40 per cent less. 

522. How is the charge of gas and air drawn into the 
cylinder of a gas engine ? 

Ans. By the suction of the piston. 

523. What precaution should be observed regarding 
the admission of the air and gas? 

Ans. The air should be pure and free from dust, and 
the gas should not contain tarry matters if it can be 
avoided. 

524. How are the induction valves usually set? 

Ans. So that the first portion of the charge is air only, 
then air and gas, and finally air with a small quantity of 
gas. 

525. How is the air valve controlling the entry of the 
entire charge adjusted? 

Ans. It is set to open well in advance of the inner dead 
center of the engine, and is kept from closing until after 
the outer dead center. 

526. Why is this valve so set? 

Ans. In order that the full effect of the momentum 
imparted to entering gases at the highest rate of piston 
speed may be utilized. 

527. Upon what does the allowable compression pres- 
sure depend? 



80 Steam Engineering 

Ans. Upon the relative proportions of hydro-carbon 
gases, and hydrogen contained in the mixture. 

528. What per cent of hydrogen is considered within 
the limits of safety ? 

Ans. Not over 7 per cent. 

529. What are the usual compression pressures carried 
with blast furnace gas ? 

Ans. 200 lbs. per sq. in. 

530. What pressure may be safely carried when pro- 
ducer gas is used ? 

Ans. From 150 to 200 lbs. per sq. in. 

531. If illuminating gas is used, what is the maximum 
safe pressure? 

Ans. 120 lbs. per sq. in. 

532. How is the cylinder cooled and cleaned? 

Ans. By the injection of water or cold air through 
the clearance spaces, and valve ports during the charging 
stroke, or by pressure during compression. 

533. What other methods are available for cooling the 
cylinder and piston rod ? 

Ans. By means of a water jacket that surrounds the 
cylinder. The piston rod may be hollow and water cir- 
culated through it. 

534. How is the charge of gas and air ignited? 

Ans. Formerly by hot tubes of porcelain or hecnum, 
which are still used to some extent, but at the present day 
electrical ignition devices are used principally. 

535. What kind of electrical devices are used for this 
purpose ? 

Ans. Primary batteries, storage batteries, and magneto 
machines, or the current may be taken from the lighting, 
or power circuit. 



The Gas Engine 81 

536. How many types of primary batteries are in com- 
mon use? 

A ns. Two— Dry and wet batteries. 

537. What are the elements commonly used in the wet 
batterv ? 

Arts. Carbon and zinc immersed in a jar or cell con- 
taining a solution of sal ammoniac, or sulphate of copper. 

538. Describe the copper oxide battery. 

Ans. It consists of a plate of copper oxide, and a zinc 
plate, both being immersed in a solution of caustic potash. 

539. What is the usual voltage of these cells? 
Am. From 1 to 2 volts per cell. 

540. Describe in brief the construction of the storage 
cell? 

Ans. It consists of gridded frames of lead, part of which 
are filled with red lead for the positive plates, and those for 
the negative plates are filled with litharge, all being im- 
mersed in a solution of 6 parts of water to 1 part of sul- 
phuric acid. 

541. How is a dry battery made? 

Ans. A round zinc case forms one of the elements, and 
a piece of carbon in the center of the case forms the other 
element. 

542. Are there any other ingredients? 

Ans. Yes — A mixture of powdered manganese, carbon, 
and flour is packed around the carbon, while the rest of the 
can is filled with a plaster mixture of oxide of zinc and 
flour, and the whole is soaked in a solution of sal ammo- 
niac and zinc chloride. 

543. In what manner does the electric current ignite 
the charge of gas in the cylinder? 



82 



Steam Engineering 



Ans. By means of the jump spark caused by alternately 
making and breaking the circuit. 

544. What is one of the most important features con- 
nected with ignition? 

Ans. To see that ignition occurs at the proper moment. 

545. At what point in the stroke of the piston should 
ignition occur? 

Ans. This depends upon the quality of the gas used. 
With the maximum allowable percentage of hydrogen, igni- 
tion should not occur until after the piston has passed the 
inner dead center. Otherwise the result will be violent 
shocks, and strains upon the working parts. 

546. Do high initial explosions create the most powerful 
efforts behind the piston? 

Ans. They do not. 

547. What are the usual terminal pressures for gas 
engines ? 

Ans. 25 to 30 lbs. above atmospheric pressure. 

548. How is the horse power of a gas engine calculated ? 

Ans. Usually from the same formula used in connec- 
tion with the steam engine, and the computation is based 
upon the mean effective pressure developed at each ex- 
plosion. 

549. What percentage of the total calorific value of 
the coal is usually converted into useful work with the 
steam engine? 

Ans. From 5 to 10 per cent. 

550. What percentage of the energy contained in the 
fuel is it possible to utilize with a modern gas-driven unit? 

Ans. From 16 to 20 per cent. 

551. How many types of apparatus are in use for the 
production of gas for power? 



The Gas Engine 83 

Ans. Three: the suction producer, the steam pressure 
producer, and the induced down draft producer. 

552. What kind of fuel must be used in the suction, 
and steam pressure producers? 

Ans. Coke, or anthracite coal. 

553. What kind of fuel is the induced down draft pro- 
! ; ducer adapted for ? 

Ans. Bituminous coal. 

554. How may gas engine efficiency be expressed? 
Ans. In terms of heat value. 

555. Is there any difference of importance between a 
| gas engine, and a gasoline or oil engine ? 

Ans. None of any importance. A gas engine may be 
ii easily converted into a gasoline engine, or vice versa. 

556. Wherein lies the principal difference between the 
s two kinds of engines ? 

Ans. In the gas engine proper the gas is supplied to 
the cylinder by the producer. In the gasoline engine the 
gas is generated within the cylinder, from a charge of 
gasoline. 

557. How may the action of the gas within the cylinder 
of a gas engine be ascertained ? 

Ans. By means of diagrams taken with an indicator. 

558. Is there any difference between a steam engine in- 
dicator, and an indicator adapted for gas engines? 

Ans. None in principle. The gas engine indicator is 
made somewhat stronger owing to the high pressures used. 

558a. What is the propelling force behind the piston 
of an oil engine? 

Ans. The heat energy evolved by the combustion of a 
mixture of vaporized fuel oil and air under compression. 
55Sb. How is the vaporization of the oil accomplished? 



84 Steam Engineering 

Ans. There are four methods classified as follows: 

(1) Vaporization caused by the heat evolved by the 
engine. 

(2) Vaporization in an external chamber which is 
heated from external sources. 

(3) Vaporization in an internal chamber heated whol- 
ly or in part from external sources. 

(4) Combustion caused by the neat of highly com- 
pressed air without previous vaporization of the oil. 

558c. Which one of these methods of vaporization has 
proved to be the most practical and best adapted to all 
conditions ? 

Ans. The one belonging in class (4) owing to its sim- 
plicity and the absence of much auxilliary equipment. 

558d. Explain the principles of a two-cycle oil engine. 

Ans. A two-cycle engine receives a charge of the ex- 
plosive mixture, compresses it, ignites it and discharges the 
products of combustion while the piston makes one com- » 
plete travel back and forth, thus giving a working stroke 
for each revolution of the crank shaft. 

558e. Explain the action of a four-cycle oil engine. 

Ans. The four-cycle engine requires four strokes of the 
piston or two revolutions of the crank shaft to complete 
the cycle; hence there is but one power stroke for every 
two revolutions of the crank shaft. 

558f. To which one of the four classes of oil engines 
as enumerated in the answer to question 558b does the 
Diesel engine belong? 

Ans. To class (4). 



Air Compressors 



559. What is one of the results of compressing air? 
Ans. The development of heat. 

560. What amount of work is lost by the development 
and dissipation of this heat? 

Arts. The work .represented by the mechanical equiva- 
lent of the heat developed. 

561. Mention another cause of more or less lost work- 
in air compression? 

Ans. Friction of the air in the pipes through which it 
is conveyed. 

562. By what two methods is air compression generally 
accomplished ? 

Ans. Isothermal, by which the heat of compression is 
carried away as fast as developed ; and adiabatic, by which 
no heat is removed from the air. 

563. Which of the two is the ideal method of com- 
pression ? 

Ans. The isothermal. 

564. Is it possible of attainment? 
Ans. Not entirely. 

565. What may be said of the adiabatic method? 
Ans. It is one which should be avoided as much as 

possible. 

566. What are the actual results secured in the best- 
compressors ? 

Ans. They are intermediate between the two methv 
ods just mentioned, but nearer to the second method. 

85 



86 Steam Engineering 

567. Upon what does the efficiency of an air compres- 
sor depend principally? 

Ans. Upon the effectiveness of the cooling devices. 

568. How many practical methods of removing the 
heat of compression are there ? 

Ans. Two — jacket cooling, and intercooling. 

569. Is jacket cooling of the compressor-cylinder ef- 
fective ? 

Ans. H"ot entirely, except with single-stage compres- 
sion. 

570. What is an intercooler? 

Ans. It is a cooling device interposed between the 
cylinders of a compound or multi-stage machine, through 
which the air passes on its way from one cylinder to 
the next one. 

571. Describe the process of compression by the multi- 
stage method? 

Ans. A multi-stage compressor has two or more cylin- 
ders, the intake or low pressure cylinder being the lar- 
gest in diameter, and in which the air is first compressed 
to a low pressure, and then passed on into the next cylin- 
der which is of smaller diameter, where the air is com- 
pressed to a still higher pressure, and so on in increasing 
ratio. 

572. How should the cylinder ratios be proportioned? 

Ans. So that the M. E. P. and the final temperature 
are equal in all the cylinders. 

573. Describe the construction of an intercooler? 
Ans. It usually consists of a nest of tubes through 

which cold water circulates, and between which the stream 
of air passes. 



Air Compressors 87 

574. Which method, single-stage, or multi-stage, ap- 
proaches nearest to the theoretical ideal? 

Ans. The multi-stage, with intercoolers. 

5. Mention another point in favor of multi-stage 
compression ? 

Ans. It permits a higher piston speed, thus econo- 
mizing in steam. 

576. What is one of the greatest difficulties encoun- 
tered in air power transmission? 

Ans. Freezing of the moisture in the air, either in 
the pipe line, or at the exhaust ports of the air motors. 

577. How may this condition he avoided to a large 
extent ? 

Ans. By the proper cooling of the air during compres- 
sion, which will precipitate the moisture, which may then 
be withdrawn by drain pipes. 

578. What would be the resultant temperature of air 
compressed from atmospheric pressure, and 60° Fahr., to 
a final pressure of 100 lbs., provided there was no cooling 
device ? 

Ans. 484° Fahr. 

579. What effect would this have upon the cylinder 
lubricant ? 

Ans. It would be burned, and be useless. 

580. What would be the temperature of the same 
volume of air if compressed in the first, or intake cylinder 
of a multi-stage machine to a pressure of 25 lbs.? 

Ans. 233° Fahr. 

581. If passed through an intercooler on its way to 
cylinder No. 2, what would its temperature be? 

Ans. It would be brought back to its original tem- 
perature of 60° Fahr. and enter the second cylinder under 
a pressure of 25 lbs. 



38 Steam Engineering 

582. What would the temperature of the same air be 
if compressed in cylinder No. 2 from 25 lbs. to 100 lbs. 
pressure ? 

Arts. It would be but little in excess of that attained 
in the first cylinder, viz., 233° Fahr. 

583. Why would it not attain the temperature stated 
in the answer to question 578, viz., 484° Fahr.? 

Arts. Because the heat of compression is a function of 
the number of compressions, and practically independent 
of the initial pressure. 

584. Why is air compression at high altitudes more ex- 
pensive than at sea level? 

Ans. Because the capacity of the compressor decreases 
in a greater ratio than does the power necessary to com- 
press. 

585. At an elevation of 10,000 ft. above sea level, 
what is the increase in expense ? 

Ans. Over 20 per cent. 

586. What should be the first care in the installation 
of an air compressor? 

Ans. To provide a suitable foundation. 

587. What precautions should be observed in the pip- 
ing? 

Ans. First, there should be as few L's as possible, and 
second, all pipes should be thoroughly cleaned before start- 
ing the compressor; third, allowance should be made for 
expansion. 

588. What is the function of the unloader on the In- 
gersoll-Eand air compressor? 

Ans. To take the load off the air piston when the pres- 
sure reaches the desired point. 

589. What is the function of the regulator? 



Air Compressors 89 

Ans. To regulate the supply of steam to the steam 
end of the compressor. 

590. What type of air inlet valves is this compressor 
equipped with? 

Ans. Piston inlet valves. 

591. Describe the action of these valves? 

Ans. The air enters and passes through the piston > thus 
tending to keep it cooled. 

592. What is the function of the Mason pump gov- 
ernor, with which some air compressors are equipped? 

Ans. To maintain a constant speed regardless of the 
load. 

593. What kind of inlet valves is the Dallett air com- 
pressor fitted with? 

Ans. Either mechanically operated valves, or auto- 
matic poppet valves, as desired. 

594. With what type of valves are the Allis-Chalmera 
air compressors usually equipped? 

Ans. Eotary valves for the inlet, and single-beat poppet 
valves for the discharge. 

595. How are the inlet valves operated? 

Ans. By an eccentric on the main shaft, and a wrist 
plate. 

596. What other type of valve-gear are some of 
these compressors equipped with? 

Ans. Both inlet, and discharge valves are actuated by 
independent eccentrics on the main shaft. 

596a. With what type of valve is the Ingersoll- 
Sargeant air compressor equipped? 

Ans. The Meyer cut-off valve gear. 

596b. Describe the construction and action of the 
discharge valves on the Allis-Chalmers air compressor. 



w 

90 Steam Engineering 

Ans. These valves are of the drawn steel cup type 
and open automatically when the pressure in the cylin- 
der equals the discharge pressure. They are mechan- 
ically closed. 

596c. How is the closing of these valves affected? 

Ans. By means of plungers actuated by the dis- 
charge pressure and so timed as to positively bring the 
valves to their seats just at the moment the piston 
reaches the end of its stroke, thus preventing any slip 
of air back past the valves, and also any slamming 
when the piston starts on the return stroke. 

596d. When the discharge valves are closed what is 
the action of the plungers? 

Ans. They recede leaving the valves held to their 
seats by the discharge air pressure until the point in the 
return stroke of the piston is reached where the pres- 
sure of the cylinder again equals discharge pressure, 
when the valves open automatically. 



Refrigeration 



597. Of what does the process of refrigeration consist ? 
Arts. In the abstraction of heat from a substance. 

598. Describe a freezing mixture that will give a tern- 
I perature of 67 degrees below zero. 

Ans. A mixture of one pound of calcium chloride, and 
1 0.7 lbs. of snow. 

599. Upon what are the theory, and practice of mechan- 
I ical refrigeration based? 

Ans. Upon the two first laws of thermo-dynamics. 

600. What is the first of these laws? 

Ans. Mechanical energy and heat are mutually con- 
vertible. 

601. Define the second law. 

Ans. An external agent is necessary to complete or 
! bring about this transformation. 

602. Is heat generated by compression, or by any other 
means ? 

Ans. It is not generated but developed, because there 
is a fixed amount of heat in the universe which can neither 
be increased nor diminished. 

603. What is the result of compressing one pound of 
air at 70 degrees temperature and at atmospheric pressure, 
to one half its original volume ? 

Ans. An increase in its static pressure, also an increase 
in its temperature. 

604. In order that the higher pressure may be main- 
tained, as the temperature is reduced, what is necessary? 

91 



92 am Engineer 

Ans. A small additional quantity of air will have to be 
forced into the compressor cylinder. 

605. If the pound of compressed air be allowed to ex- 
pand in a cylinder what will be the result? 

Ans. A portion of the heat developed by compression 
will be given up. 

606. What can be said of the mechanical work done 
by this air in its expansion? 

Ans. In amount it is exactly the same as that done upon 
it during its compression. 

607. How is the temperature of a body or substance 
reduced ? 

Am. >By transferring more or less of the heat con- 
tained in the body to some other substance or body. 

608. What work is demanded of a refrigerating ma- 
chine? 

Ans. To extract heat from a body, and by the expendi- 
ture of mechanical energy to sufficiently raise the temper- 
ature of this heat to admit of its being carried away by a 
suitable external agent, usually water. 

609. How may a refrigerating machine be defined, and 
what is its main function? 

Ans. As a heat pump, its main function being the 
abstraction of heat from the body to be cooled, and trans- 
ferring that heat to a cooling agent. 

610. How may the various devices for refrigeration and 
ice making be classified? 

Ans. Under five principal heads. 

611. Explain the action of apparatus belonging to 
class one. 

Ans. Heat is abstracted from the body to be cooled, 
by the dissolution or liquefaction of a solid, as for instance 
the cooling of water with ice. 



Refr igeration 9 3 

612. Describe the vacuum system? 

Arts. The abstraction of heat is effected by the evapora- 
tion of a portion of the liquid to be cooled, the process 
being assisted by an air pump. 

613. How is refrigeration effected in machines belong- 
ing to the third class? 

Arts. By the evaporation of a separate refrigerating 
agent, which is subsequently restored to its original physi- 
|| cal condition by mechanical compression and cooling. 

614. Describe the fourth or absorption system. 
Arts. Heat is abstracted by the evaporation of a sepa- 
rate refrigerating agent, under the direct action of heat 5 

!j which agent again enters in solution with a liquid. 

615. Describe the action of machines belonging to the 
! |! fifth class, known as cold air machines ? 

Ans. Air, or other gas is first compressed, then coaled, 
and afterwards permitted to expand while doing work. 

616. What two systems have come into general use in 
the United States? 

Am. The ammonia compression system, and the am- 
monia absorption system. 

617. What are the three distinct stages in the com- 
pression system? 

Aiis. Compression, condensation, and expansion. 

618. What is the refrigerating agent or medium used 
in the compression system ? 

Arts. Anhydrous ammonia. 

619. Of what does ammonia consist, and what is its 
chemical formula? 

Ans. One part of nitrogen, and three parts of hydro- 
gen. Its chemical formula is NH 3 . 

620. Under what two conditions may gaseous ammonia 
be liquefied? 



94 Steam Engineering 

Ans* At a pressure of 128 lbs. per sq. in., and a tem- 
perature of 70° Fahr., or a pressure of 150 lbs. and a tem- 
perature of 77° Fahr. It may also be liquefied by cold if 
its temperature be reduced to 85.5° Fahr. below zero. 

621. To what pressure is gaseous ammonia usually 
compressed ? 

Ans. From 125 to 175 lbs. per sq. in. 

622. Of what does a compression plant consist? 

Ans. Of a high pressure system made up of a condens- 
ing coil surrounded by cooling water, and a low pressure 
system consisting of an evaporating coil surrounded by 
brine, or open to the room to be cooled. 

623. What takes place during compression? 

Ans. The latent heat of the vapor is converted into 
active, or sensible heat. 

624:. How is the vapor condensed, or liquefied? 

Ans. It is forced into and through the condenser coils 
which are submerged in a body of cold water, or over which 
cold water is flowing, and the sensible heat developed dur- 
ing compression is thus transferred to the cooling water. 

625. How are the refrigerating qualities of the am- 
monia in its liquefied state utilized? 

Ans. It is allowed to pass in small quantities from the 
condenser into pipe coils placed in the rooms to be cooled, 
when it again expands into a vapor, and takes up an 
amount of heat exactly equivalent to that given up during 
condensation. 

626. After being expanded into vapor, what becomes 
of it? 

Ans. It is drawn back into the compressor, again com- 
pressed, condensed, and expanded, the cycle of operations 
being repeated indefinitely. 



Refrigeration 95 

627. How man} 7 , and what are the systems of refrigera- 
tion by compression? 

Ans. Two — the wet system, and the dry. 

628. Describe the theory of the wet system. 

Ans. The ammonia vapor is cooled by the injection 
into the compressor cylinder of a small quantity of liquid 
!; ammonia at the beginning of each stroke, and it is carried 
lj from the cooling room back to the compressor in a sat- 
urated state. It is thus kept in contact with a small por- 
tion of its originating fluid, and is kept comparatively cool. 

629. Upon what does the pressure of steam in a boiler 
|| depend ? 

Ans. Upon its temperature, which is always the same as 
i| that of the water in the boiler. 

630. What are the relations of temperature and pres- 
sure in the case of steam while in contact with the originat- 

i ing water? 

Ans. They are interdependent. 

631. What is the result if the steam is superheated* 
Ans. It may still be of the same pressure, but its tem- 
perature will be higher. 

632. What results from the compression of a dry gas 
without cooling? 

Ans Its temperature may be much higher than that 
corresponding to its pressure. 

633. What does the Adiabatic curve as traced bv the 
indicator represent? 

Ans. The compression, or expansion of a gas without 
loss or gain of heat. 

634. Describe in brief the construction of the cylinder 
heads, and valves in the Linde ice machine. 



96 Steam Engineering 

Ans. The piston and cylinder heads are spherical, and 
of the same radius, and the valve discs conform to this 
radius. 

635. What is the clearance between piston and cylin- 
der head ? 

Ans One thirty-second of an inch. 

636. How is the piston lubricated ? 

Ans. In a large measure by the moisture in the am- 
monia vapor. 

637. In the De La Yergne refrigerating machine how 
is the heated gas cooled ? 

Ans. By passing it through coils of pipe surrounded 
by running water. 

638. How many valves has the Triumph ice machine? 
Ans. Five, three suction valves, and two discharge 

valves. 

639. What advantage is said to be gained by the use 
of the third suction valve? 

Ans. That it tends to increase the economy of the ma- 
chine. 

640. Describe the construction of a double pipe am- 
monia condenser. 

Ans. It consists of two series of coils, one within the 
other. 

641. How many methods are there of utilizing refrig- 
eration ? 

Ans. Two; the brine system, and the direct expansion 
system. 

642. Describe in brief the brine system. 

Ans. The coils of pipe in which the ammonia is ex- 
panded are submerged in a solution of salt, or calcium 
chloride. This brine after beins: reduced to a low tempera- 



Refrigeration 97 

ture is pumped through coils of pipe in the rooms to be 
cooled. 

643. Describe the direct expansion system. 

Ans. The expansion coils are placed in the rooms to be 
cooled, and the cooling is effected directly by the expansion 
of the ammonia. 

644. Which one of the two systems is the most efficient ? 
Ans. The direct expansion system. 

645. Mention a few of the advantages that this system 
has over the brine system. 

Ans. First — All intermediate agencies are dispensed 
with. Second — The whole plant is much simpler. Third 
— A larger expansion surface. 

646. By what two systems is ice made or manufactured ? 
Ans. The can system and the plate system. 

647. Mention other refrigerating agents besides am- 
monia that may be used in the compression system ? 

Ans. Ether, methyl-chloride, sulphurous acid, and car- 
bonic acid. 

648. How is refrigeration effected in the absorption 
system ? 

Ans. By the continuous distillation of ammoniacal 
liquor. 

649. What advantage appertains to the absorption 
system ? 

Ans. The bulk of the heat required for the work is 
applied direct without being transformed into mechanical 
power. 

650. What pressure is usually maintained in the gen- 
erator ? 

Ans. 150 lbs. per sq. in. 

651. Mention the more important features of the ab- 
sorption machine? 



98 Steam Engineering 

Ans. The expansion valve, the absorber, and the 
strength of the liquor. 

652. Upon what does the efficiency of the machine 
mostly depend? 

Ans, Upon the condition of the absorber. If it is cool 
and free from air, or poor gas, better results will be 
realized. 

653. What should be done if one side of the absorber 
should get warmer than the other ? 

Ans. The spray valve should be turned down slightly, 
say one-eighth of a turn. 

654. Mention one of the troubles in the operation of 
this system. 

Ans. A filling up of the coils with scale and dirt. 

655. What is the remedy in such cases? 

Ans. Stop the machine once a week, drain the coils, and 
blow them out with compressed air. 

656. How is anhydrous ammonia formed? 

Ans. By condensing ammonia gas to a liquid, and 
applying pressure. 

657. Under atmospheric pressure, what is the boiling 
point of anhydrous ammonia? 

Ans. 28.5 degrees delow zero Fahr. 

658. What is the specific gravity of liquid ammonia 
compared with water? 

Ans. At 32° Fahr. it is about % that of water, or 
0.6364. 

659. What is its latent heat of evaporation? 

Ans. At 32 degrees temperature it is 560 thermal units. 

660. If evaporated at 32° Fahr. and atmospheric pres- 
sure, how much space will one pound occupy? 

Ans. Twenty-one cubic feet. 



Elevators— Electric and Hydraulic 

661. What are the essential parts of the Otis traction 
elevator ? 

Ans. A traction motor driving sheave, and a pair of 
electrically released brake shoes. 

662. What type of electric motor is used in the Otis 
traction elevator? 

Ans. A slow speed shunt-wound motor. 

663. What is the principal function of the armature 
shaft besides carrying the armature? 

Ans. To support the load, 

664. How, then, is the drum, or sheave driven? 
Ans. By means of projecting arms from the armature, 

that engage with similar arms projecting from the drum. 

665. Describe the system of safety devices with which 
this elevator is equipped? 

Ans. There are two groups of switches located respec- 
tively at top and bottom of the shaft, each switch in series 
being opened one after the other by the car as it passes. 
This retards the speed and finally brings the car to stop, 
applying the brake, independent of the operator in car. 

66Q. Are there any other safeties besides this ? 

Ans. Yes — speed governors, wedge clamps for gripping 
the guides, and potential switches. 

667. Describe in general terms the construction of the 
Otis geared traction elevator? 

Ans. A multi-grooved driving sheave around which the 
cable works. The sheave is mounted upon a shaft driven 

99 



100 Steam Engineering 

hy geared wheels actuated by a right and left hand worm 
cut on the armature shaft. 

668. What advantage is gained by the use of the double 
screw, or worm ? 

Arts. The elimination of all end thrust. 

669. "With what kind of brake is this machine equipped? 
Ans. A mechanically applied, and electrically released 

brake. 

670. What type of motor is used? 

Ans. Compound-wound — speed 800 E. P. M. 

671. When is the series field of this motor used? 
Ans. Only at starting. 

672. Why? 

Ans. To obtain a highly saturated field in the shortest 
possible time. 

673. How is a gradual slowing down of speed of car 
obtained with this elevator? 

Ans. By throwing a low resistance field across the ar- 
mature, thus providing a dynamic brake action. 

674. What kind of current is used for operating elec- 
tric elevators? 

Ans. Either alternating, or direct current. 

675. How is the transmission of current to the motor 
of an electric elevator controlled ? 

Ans. By means of an electric magnet controller op- 
erated through the switch in the car. 

676. How may considerable power be wasted in the 
operation of electric elevators? 

Ans. By careless handling — making unnecessary stops 
and starts, or too sudden stops or starts. 

677. Briefly, of what does the mechanism of a hydraulic 
elevator consist? 



Elevators — Electric and Hydraulic 101 

Arts. A cylinder and piston with one or more rods con- 
nected to a crosshead which carries the sheaves over which 
rim the lifting cables from which the car is suspended. 

678. What moves the piston? 

Arts. Water under pressure admitted by means of suit- 
able valves causes the piston to move from one end of the 
cylinder to the other, and back again. 

679. How is this motion transmitted to the elevator 
car? 

Ans. By means of the sheaves mounted on the cross- 
head which carry the lifting cables. 

680. In what position is the cylinder placed ? 

Ans. Either vertical alongside the hatchway, or hori- 
zontal in the basement of the building. 

681. How are the valves of a hydraulic elevator op- 
erated ? 

Ans. In some cases by a hand rope passing through 
the car and over small sheaves at the top and bottom of 
the hatchway, and connected with the main valve in the 
basement. By pulling this rope down the valve is opened, 
and the car will ascend, while pulling the rope up will 
cause the car to descend. 

682. What safety devices are attached to this type of 
elevator ? 

Ans. Two balls are attached to the hand rope, one near 
the bottom, and the other near the top. These balls come 
in contact with the top, or bottom of the car, according 
as it is going up or coming down, and being carried along 
they, of course move the cable, thus actuating the valve, 
bringing the car to a stop. 

683. Is this device safe, and automatic? 
Ans. It is. 



102 Steam Engineering 

684. Mention another safety device connected with 
hydraulic elevators. 

Ans. Safety clamps under the control of a speed limit 
centrifugal governor which causes the clamps to grip the 
guides and thus hold the car. 

685. How is this safety governor operated ? 

Ans. By means of a small cable connected with the car 
and moving with it, which passes over the sheave pulley 
of the governor. 

686. Why are some elevator pistons fitted with two pis- 
ton rods? 

Ans. To prevent the piston, and crosshead from turn- 
ing or twisting, and also to strengthen the construction. 

687. What other methods are used for manipulating 
the water valve, besides the one already described? 

Ans. Banning ropes, and standing ropes, either of 
which may be operated by means of a lever, or wheel in 
the car. 

688. Do these devices directly operate the main valve? 
Ans. No. They operate a small valve called the pilot 

valve. 

689. What is the function of the pilot valve? 

Ans. When opened it admits the pressure water to a 
small cylinder with piston connected to the main valve 
stem. This actuates the main valve, which in turn, by its 
movement, closes the pilot valve. 

690. Upon what does the amount of opening given the 
pilot valve, and consequently the main valve depend? 

Ans. Upon the distance the lever in the ear is moved 
from central position. 

691. What is meant by central position of lever? 



Elevators — Electric and Hydraulic 103 

Arts. That position in which there is no flow of water 
either into or out of the cylinder, and the car is moving 
only by its momentum. 

692. What is the result of moving the lever too quickly 
to central position when the car is moving at a high 
rate of speed? 

Arts. The motion of the car will be arrested with a 
sudden jerk. 

693. How many kinds of horizontal hydraulic elevators 
are in use? 

Ans. Two. One is the pushing, and the other the 
pulling type, 

694. Describe the action of the pushing type? 

Ans. The car being at the bottom, the pressure water 
is admitted behind the piston which then moves, pushing 
the crosshead and cable sheave and lifting the car. 

695. Describe the action of the pulling type? 
Ans. It is the opposite of that just described. 

696. Is there much difference in the valve mechanism 
of the horizontal, and vertical types of hydraulic elevators ? 

Ans. Very little except a few minor details. 

697. What is meant by a double-deck machine? 

Ans. Where the floor space is restricted two, and some- 
times three or four machines are mounted one above the 
other. 

698. What water pressure is usually carried in operat- 
ing the types of hydraulic elevators that have hitherto 
been described? 

Ans. Pressures not exceeding 200 lbs., the average being 
150 lbs. per square inch. 

699. Are any higher pressures than this being used for 
operating hydraulic elevators ? 

Ans. Yee. Pressures of 700 to 800 lbs. and higher. 



104 Steam Engineering 

700. Why are such high pressures used? 

Ans. Owing to increased height of buildings, and the 
demand for high car speed. 

701. What advantage, other than high speed, is gained 
by the use of high pressure elevators? 

Ans. A reduction in the size of the valve mechanism, 
piston areas and piping. 

702. Mention another advantage in connection with 
the high pressure system? 

Ans. A reduction in the loss by friction of the water 
passing through the pipes, owing to reduced areas. 

703. What is the percentage of loss due to this cause? 
Ans. In low pressure machines from 10 to 30 per 

cent, and in high pressure machines from 5 to 6 per cent. 

704. Describe in general terms the construction of the 
cylinder and piston of a high pressure machine. 

Ans. The cylinder area is reduced to about one-eighth 
that of the low pressure type, and the piston is a solid 
plunger. 

705. How is the pressure maintained? 

Ans. The pump forces water into the lower end of the 
accumulator, an air-tight tank, which is also weighted. 
From the accumulator a pipe runs to the main valve. 

706. Describe in general terms the construction and 
operation of the direct-acting plunger elevator. 

Ans. A cylinder is set vertically in the ground under 
the center of the car, and the length of it is slightly 
greater than the travel of the car. In this cylinder is a 
plunger of the same length, which carries the car. Water 
under pressure is forced into the cylinder and thus lifts 
the car, and allowed to run out at the top when the car 
descends. The cylinder is about two inches larger in dia- 
meter than the plunger, and is always full of water. 



Elevators — Electric and Hydraulic 105 

707. What is the usual diameter of the plunger? 
Ans. 6% to 7 inches. 

708. How is it constructed? 

Ans. Of lengths of highly polished steel pipe, joined 
together with an internal sleeve, and having its lower end 
closed. 

709. What pressure is ordinarily used on this type of 
elevator ? 

Ans. 150 to 200 lbs. per square inch. 

710. How is the top of the cylinder arranged? 

Ans. With a packing gland through which the plunger 
moves up and down. 

711. What types of elevators are in general use for 
passenger service? 

Ans. Electric and hydraulic. 

712. How is the capacity of a pump usually expressed? 
Ans. In gallons of water per minute raised to a given 

height. 

713. What is meant by the head under which a pump 
works ? 

Ans. The vertical distance between the surface of the 
water in the suction reservoir, and that in the discharge 
reservoir. 

713a. How may the useful work of a pump be calcu- 
lated in terms of horse power? 

Ans. Weight of water in pounds per minute multi- 
plied by height in feet to which it is raised, divided by 
33,000 equals horse power developed by the pump. 



106 



Steam Engineering 




fig. 512 




FIG. 514 



Electricity for Engineers 

714. What is electricity? 

Ans. Electricity is an invisible agent. Its exact na- 
ture is not very well known, although the laws govern- 
ing its action, the methods of controlling it, and the ef- 
fects produced by it are becoming well known. 

715. Is it correct to use the term quantity with refer- 
ence to electricity? 

Arts. It is. We may use terms to designate definite 
quantities of electricity, passing through a conductor, in the 
same way that we speak of gallons of water flowing through 
a pipe. 

716. Is it proper to assume that there are large quanti- 
ties of electricity stored for future use, in a manner similar 
to water? 

Ans. It is not, except in a limited sense, as in storage 
batteries. 

718. Define the doctrine of the conservation of energy. 

Ans. The total quantity of energy in the universe is 
unalterable. When energy is expended, or disappears in 
one form, it must reappear in another form. 

719. In accordance with this doctrine, what would be 
the proper term to apply to electricity with reference to 
the physical requirements of man? 

Ans. It is a useful agent for the rapid transmission of 
stored up energy in fuel, water falls, etc. 

720. What is the practical unit of quantity used in 
speaking of electricity? 

107 



108 Steam Engineering 



Ans. The coulomb. It is that quantity of electricity 
that would pass in one second through a circuit carrying a 
current of one ampere. 

721. What is an ampere? 

Ans. It is the unit of volume, or rate of flow. A cur- 
rent of one ampere will flow through a circuit whose re- 
sistance equals one ohm, when the electro-motive force, or 
pressure behind it equals one volt. 

722. What is a volt? 

Ans. The volt is the unit of electro-motive force, and 
represents a pressure that will cause the flow of one am- 
pere through a circuit in which the resistance equals 
one ohm. 

723. What is an ohm? 

Ans. The ohm is the practical unit of electrical resist- 
ance. It is that amount of resistance that would limit the 
flow of electricity under an electromotive force of one 
volt, to a current of one ampere, or to a discharge of 
one coulomb per second. It equals the resistance of a 
column of mercury one sq. millimetre in area of cross sec- 
tion, and 104.9 centimetres in length. 

724. What is the unit of work? 
Ans. The foot pound. 

725. What is the unit of power, or rate of doing work ? 
Ans. The foot pound, per second. 

726. How is the amount of work that electricity is ca- 
pable of doing, measured ? 

Ans. By the volt-coulomb, or Joule. The amount of 
electrical work per second is equal to the volt ampere, or 
watt. 

727. What amount of power developed is represented 
by the watt ? 



What is Electricity 109 

Ans. 44.25 foot-lbs. of work per minute, or 0.7375 foot- 
lbs, per second. 

728. What is a magnet? 

Ans. A mineral consisting of a combination of iron and 
oxygen. 

729. What is the chemical formula of a magnet? 
Ans. Fe 3 4 . 

730. What is a permanent magnet? 

Ans. A piece of steel that has been charged with mag- 
netism, and retains it. 

731. What is meant by the poles of a magnet? 

Ans. All magnets tend to point north and south, the 
same end always pointing in the same direction ; hence the 
end pointing north is called the north pole, and the end 
pointing south is termed the south pole. 

732. What peculiar characteristic attaches to the poles 
of magnets ? 

Ans. The north poles of two magnets tend to repel 
each other, and the same is true of the south poles. But 
the north pole of one magnet attracts the south pole of an- 
other, like repels like, and unlike attracts unlike. 

733. What is an electro magnet? 

Ans. A bar of iron surrounded by a coil of wire through 
which an electric current is passing. 

734. What are lines of force? 

Ans. They are certain imaginary lines passing through 
the steel of the magnet from its south pole to its north pole, 
and issuing from the latter they curve around through 
space and return to the south pole. 

735. What is the magnetic circuit? 

Ans. It is the path of these lines of force, around and 
through the magnet. It resembles a closed curve, either a 
circle, or an ellipse. 



110 Steam Engineering 

736. Explain the difference between the magnetic cir- 
cuit and the electric circuit. 

Ans. The magnetic circuit, or field of foree, that sur- 
rounds a magnet is maintained without the expenditure of 
energy, while on the other hand an electric current passing 
upon its circuit develops energy, and energy must be ex- 
pended to maintain it. 

737. Are there any other points of difference between 
the two circuits. 

Ans. Yes, the electric current passes through a con- 
ductor in intensity proportional to the electro-motive force 
urging it, while the magnetic circuit passes through air. 
or a vacuum in proportion to the magneto-motive force 
urging it. 

738. What is meant by the term potential as applied in 
electric practice? 

Ans. Voltage or pressure. 

739. What is the law of induction? 

Ans. When a conductor is moved in a magnetic field 
of force so as to cut the lines of force, there is an electro- 
motive force impressed on the conductor in a direction at 
right angles to the direction of motion, and at right an- 
gles to the direction of the lines of force. 

740. What is a dynamo? 

Ans. A machine for transforming mechanical energy 
into electrical energy. 

741. How is the field of force maintained in a dynamo? 
Ans. By means of electro-magnets. 

742. Does not this require the expenditure of energy? 
Ans. Yes : a certain amount of energy is indirectly ex- 
pended. 

743. How are dvnamos classified? 



The Dynamo 111 

Ans. Into two grand divisions, viz., direct current dy- 
iiamos and alternating current dynamos. 

744. What is direct electrical current? 
Ans. A current of unchanging direction. 

745. What is an alternating current? 

Ans. A current that reverses its direction of flow, pe- 
riodically, from 20 times and upward per second. 

746. Name the principal constituent parts of a dy- 
namo. 

Ans. The armature, the field, the collecting rings, or 
commutator, and the brushes. 

747. How is electro motive force or current induced in 
a dynamo? 

Ans. By rapidly changing field and armature relations 
by means of mechanical energy. 

748. How is the output of a dynamo stated ? 

Ans. In Kilowatts equal to 1,000 X volts X amperes. 

749. How is the output of a motor stated ? 

Ans. In horse power, equal to Watts intake~746X ef- 
ficiency expressed decimally. (Not as a percentage.) 

750. What is the voltage of a dynamo? of motor? 
Ans. It is the pressure that the generator or alternator 

delivers at its own terminals. The voltage of a motor is the 
voltage which should be applied to its terminals in order 
to develop full horse power. 

751. What is full load current of dynamo? of motor? 
Ans. Full load current of a dynamo is that current 

which may be drawn steady for 24 hours without causing 
any part of the machine to exceed a safe temperature, i. e.^ 
150° Fahr. This applies to factory motors. 

752. What is meant by the rating of a dynamo? Of & 
motor? 



112 Steam Engineering 

Arts. The product of full load current multiplied by 
the voltage expressed in Kilowatts is rating of a dynamo. 
The actual mechanical horse power developed at the pinion 
of the motor as tested in shop. 

753. What is the armature core? 

Ans. The sheet iron body which carries the armature 
winding, and conducts the flux from pole piece to pole piece. 

754. What is the armature spider ? 

Ans. The casting consisting of hub and arms which 
supports armature core. 

755. What are binding wires ? 

Ans. They are narrow bands of phosphor bronze wire 
placed around the armature every three or four inches to 
help bind the winding to the core. They rest on strips of 
mica, and are sweated with solder all around. 

756. What are commutator segments? 

Ans. The commutator segments or bars are the copper 
pieces of which the commutator is built. 

757. What are commutator leads? 

Ans. They are the ends of the armature winding ex- 
tending from the core to the lug of the commutator bar. 

758. What are pole pieces ? 

Ans. The end of the magnet core nearest the armature. 
Usually larger than the core. 

759. What are magnet cores? 
Ans. The iron inside the field coil. 

760. What is the yoke? 

Ans. That part of the magnetic circuit connecting 
the magnet cores. 

761. What is the pitch of an armature winding? 

Ans. It is the number of teeth between the two sides of 
a formed coil plus one tooth. 



The Commutator 113 

Example: The two sides of a coil are in slots number 
3 and 17, then pitch is 14. 

762. Is there insulation between winding and core? 
Arts. Tes. Mica or fuller board ; there is also the tape 

on coil. 

763. What insulation is there between conductors of 
winding? 

Ans. The double cotton covering of each wire makes 
four thicknesses between conductors. 

764. What is the air gap? 

Ans. It is the air space between armature and pole 
pieces. In dynamos it is made as small as possible for ef- 
ficiency. 

In motors it is not made too small because this tends to 
make the machine spark due to the weak field. In D. C. 
series motors it is from % to *4 of an inch, in A. C. series 
motor it is smaller, say 1/10 to % inch. 

The larger the air gap of a motor the more the bearings 
may wear before there is danger of the armature rubbing 
against the lower pole pieces. 

765. What are field spools? 

Ans. The brass shells on which the field coils are 
wound. 

766. What is the commutator? 

Ans. It is a series of copper bars placed parallel to 
the shaft, insulated from each other and from the frame of 
the machine. Each is connected to the winding and cur- 
rent flows from the winding through them to the brushes. 
It at the same time reverses the connections between the 
brushes and the winding at the proper times so that the 
brush always collects current. 

767. What is a collector or slip ring? 



114 Steam Engineering 

Ans. A collector consists of two or more rings of copper 
placed around the shaft and insulated from it, and each 
other. Each is connected to a part of the winding The? 
brushes rest on the rings. 

They are used to collect current from a revolving arma- 
ture style of alternator, to feed current into armatures of 
rotary converters, or the revolving fields of alternators. 

The collector has no corrective influence and passes on 
the A. C. or D. C. current exactly as it receives it. 

Single phase machines have two rings: two, three, and 1 
six phase machines have three rings. 

768. Is there a difference between no load and full loadi 
voltage of dynamos ? 

Am. Yes. A shunt dynamo gives highest voltage at no , 
load and lowest at overloads ; the series dynamo gives lowest * 
at no load and highest at full load. The compound dy- 
namo is a combination of series and shunt, and gives same 
voltage at all loads. 

An alternator acts like a shunt dynamo. 

769. What is a field rheostat? 
Ans. it is a resistance in the field circuit which can be 

varied to change the current, and hence the field strength. 
This alters the voltage of the dynamo. 

770. What are commutated fields ? 

Ans. In some motors the field coils are arranged in sec- 
tions so that they may be arranged in parallel, or series, or 
in combinations. 

All coils in parallel give the greatest current and hence 
slowest speed of motor; all coils in series give the weakest 
field and the fastest speed. 

771. What relation has field strength to the speed of 
motor ? 






Armature Winding 115 

Ans. The weaker the field the faster the speed, for the 
motor must revolve fast to generate its proper counter 
j E. M. F. 

772. What relation has armature strength to the speed 
j| of motor ? 

Ans. The greater the armature current the higher the 
I speed. 

773. What effect on the power of a motor does field, 
i and armature strength have ? 

Ans. The greater the field and armature current the 
greater the power. 

774. What is a ring winding? 

Ans. One which passes over and under around the core, 
a space being left between the shaft and core to accommo- 
date the winding. 

775. What is a drum winding? 

Ans. One where all winding is on the outer surface of 
the core. 

776. Upon what does sparkless commutation of current 
depend ? 

Ans. (1) The more commutator bars the better, there 
being less voltage and therefore tendency to spark between 
bars. The average railway motor has from 100 to 125 
bars on commutator. 

(2) The fewer the ampere turns on the armature in 
comparison to the ampere turns on the field the less spark- 
ing. 

(3) The more turns short-circuited by the brush when 
touching two or more bars at once, the greater the tendency 
to spark. 

777. What is a shunt field? 

Ans. One whose coils are placed as a shunt across the 
brushes. It carries a small current. 



11€ Steam Engineering 

778. What is a series field? 
An#. One which carries the main, or nearly all the 

main current., and is placed in series with the armature. 
A small strip of resistance metal is used sometimes to di- 
vert a portion of the main current from the series field. 

779. What are Foucault, or eddy currents? 

Ans. Local current- set up within the armature, and l 
acting as a hindrance to the generation of useful current. 

780. How may the electro-motive force be increased ? 
Ans. By increasing the speed, or by adding more turns 

loops of wire to the armature winding. 

781. What is meant f excitation of a dynam 
Ans. When the dynamo is standing still, the field mag- 
nets become weakly magnetic, but when the armature begins 
to revolve a few volts of i current will be sent through 
the field coils, gradually g the magnetic strength 
until full voltage is r: 

782. What is a >? 
Ans. One in which the same current that travels the 

main circuit also traverses the field. 

783. Explain the action of the shunt dynamo. 
Ans. The field circuit is a shunt, and only a portion of 

the main current passes through it. 

784. How are the fields of a compound dynamo ex- 
cited? 

Ans. The fields have two distinct windings: one shunt, 
and the other series. 

?S5. What advantage pertains to the compound wound 
dynamo? 

Ans. It is practically self-regulating. 

786, What is the difference between the dynamo and 
the electric motor ? 



The Currents 1.17 

Ans. Practically none in the principles governing the 
design of the machines. Any dynamo may be used a« a 
motor, and vice versa. 

787. State the difference in their functions. 

Ans. The dynamo converts mechanical energy into elec- 
trical energy, while the motor converts electrical energy 
into mechanical energy. 

788. Upon what does the power to be obtained from 
a motor depend? 

Ans. Two things, viz., the current flowing in its arma- 
ture coils, and the strength of magnetism developed in its 
fields. 

789. How is the speed of motors controlled? 
Ans. By a starting box or rheostat. 

790. How may the direction of rotation of a motor 
be reversed? 

Ans. By reversing the current through either the ar- 
mature or the fields. 

791. Upon what principle does the alternating current 
motor act ? 

Ans. Upon the principle of induction, having for its 
main accessory the rotary field. 

792. How is a rotary field produced? 
Ans. By the use of polyphase currents. 

793. Explain the meaning of the term rotary field. 
Ans. In a rotary field the rotary action is purely elet- 

trical, the poles simply rotating around the circle. Thene 
is no rotation of the mechanism of the field. 

794. What then is a revolving field? 

Ans. A field that revolves around an axia like a wheel. 

795. What is the leading characteristic of the direct 
current ? 



118 Steam Engineering 

Ans. It travels in the same direction of pressure. 

796. What is the tendency of the current generated in 
all dynamos? 

Ans. It is alternating in voltage or pressure. 

797. Explain the meaning of the term alternating as 
used in this connection. 

Ans. The current starts at a value of zero, rises to a 
maximum of polarity, descends to a value of zero again, and 
changing in direction of pressure, rises to a maximum of 
opposite polarity, from whence it drops to zero again. 

798. How then is direct current produced from this al- 
ternating current? 

Ans. Bv means of the commutator and brushes on the 
direct current generator. 

799. What is the leading characteristic of the alternat- 
ing current? 

Ans. Its voltage is continually changing at regular in- 
tervals from zero to maximum in the direction of opposite 
polarity. 

800. How is this action best represented? 

Ans, By wave curves drawn above and below a horizon- 
tal line representing zero. 

801. In what manner does the action of the alternating 
current affect the circuit through which it travels ? 

Ans. The whole circuit passes simultaneously through 
voltage values of the cycle represented by the wave curve. 

802. What is meant by the frequency of an alternating 
current? 

Ans, The number of waves or cycles per second. 

803. What does a frequency of 60 mean? 



The Voltage 119 

Arts. It means that the voltage values pass through a 
complete cycle in one sixtieth of a second, that is 60 cycles 
per second. 

804. What is meant by alternations? 

Ans. The number of reversals per minute in the di- 
rection of pressure. 

805. How many alternations would there be in a cur- 
rent having a frequency of 60 ? 

Ans. 7,200. 

806. What is meant by a "period?" 

Ans. The time in seconds or fractions of a second re- 
quired to pass through a complete cycle. 

807. What is meant by current wave? 

Arts. It means the actual values of the current as shown 
by the volt-meter and ammeter. 

808. Do these equal the values of the theoretical wave 
curve ? 

Ans. They do not, reaching about 70 per cent. 

809. Why is this? 

Ans. It is due to the influence of the iron magnetic 
circuit caused by the connections of induction motors, arc 
lamps, and other electrical apparatus. 

810. What is meant by effective current? 

Ans. The voltage and volume as shown by the volt- 
meter and ammeter. 

811. In what respect is the maximum voltage as shown 
by the calculated wave curve useful? 

Ans. It is useful in testing insulating materials. 

812. What is meant by phase in electric practice? 
Ans. It denotes the relative position of a curreDt wave. 

with respect to the wave of electro-motive force producing 
it. 



130 Steam Engineering 



813. When is a current in phase? 
Arm. When the two waves just mentioned start at zero 

and reach their maximum values at the same instant. 

814. What is meant by lag? 
Ans. When the current wave lags behind the voltage 

wave. 

815. What is meant by lead? 
Ans. When the current wave is ahead of, or leads the 

yoltage wave. 

816. What is the meaning of two and three phase cur- 
rents? 

Ans. When the winding of the armature is such that 
two or three electro-motive forces in quadrature with each 
other are simultaneously produced by the generator the cur- 
rente thus produced may be distributed over four or six 
conductors, a pair for each current. 

817. Is it necessary to have a pair of conductors for ) 
each current in two and three phase current work ? 

Ans. No. By means of the Y winding it is possible to 
diufcrUmte the current over three wires, each wire acting as « 
a owkhu and return wire for one of the others. 



Armature Design and Construction 

818. Can the properties of a dynamo be accurately cal- 
culated from any of the formulas given for that purpose? 

Arts. No. The accurate design of a new type of dynamo, 
and an armature as well, is as much a matter of experiment 
as it is of calculation. 

819. Why is this? 

Ans. There are so many factors involved in the calcu- 
lation that cannot be accurately determined until a ma- 
chine of the exact dimensions of the one under considera- 

!| tion has been built. 

820. What are the principal factors that are so trouble- 
Li some to determine? 

Ans, The permeability of the iron, the resistance of 
the magnetic circuit, the tendency to leakage of the lines 
of force, the exact proportion of the dead wire, the reaction 
of the armature, the losses due to Foucault currents. 

821. Are not the causes of all these losses well under- 
stood ? 

Ans. They are, and it is easy enough to tell what must 
be done to lessen any or all of them. It is merely their 
exact value which is indeterminate until the machine in 
question is in operation. 

822. What is the chief precaution which must be taken 
on this account. 

Am. It is necessary to leave some part of the controlling 
influences so that they can be readily varied and thus adjust 
the machine so that it will be exactly right when it is finally 
finished. 

823. How can this best be done? 
Ans. Since it is manifestly very troublesome to rewind 

121 



122 Steam Engineering 

an armature, if perchance too great or too small a numbed 
of wires have been placed upon it, the proper factors to be 1 
arranged to be variable are : the speed, and the strength oi 
the field. In some cases the speed, even, is not changeable, 
and the whole duty of compensating for misjudgment in 
the calculations falls upon variations of the field strength, 

824. Can the whole regulation be accomplished in this 
way? 

Am. It can, and in most cases this is the method relied 
upon. It is very easily accomplished by this method if w^ 
arrange to have the fields magnetized to only a low degree 
of saturation. By doing this, however, we are led to provide 
field magnets whose capacity is far in excess of what we 
believe to be necessary and, therefore, more expensive. So 
that again in the last consideration it behooves us to experi- 1 
ment before we definitely determine the exact proportion! 
of our dynamo or motor. 

825. Are there any formulae that can be used in deter- ] 
mining the exact proportions? 

Ans. There are, and they are given below. These will I 

materially assist the student in forming an idea how thejj 

different parts can be adjusted to bring about the desired I 

final result. For the following formulae we shall adopt the I 

attached set of symbols : 

Let F=the total number of lines of force, or flux, 

V— the number of volts to be generated, 

S=the number of slots in the armature, 

R.P.S.=the number of revolutions per second, 

W=the number of wires per slot. 

Then, to find the number of wires necessary per slot where 

the speed and flux are fixed : 

10 8 XV 

W= 

PXSXRP.S. 



L 



Formulae 123 

rp find the necessary speed where the number of wires, and 
Ihe flux, are fixed: 

E. p. g.=: C: — 

FXSXW 

"To find the necessary strength of field, where the wires 
land speed are fixed : 

10 8 XV 

Tp __ 

I ~SXK.RS.XW 

ffo find the volts generated : 

_FXSXWXB.P.S. 



10 s 

826. Are these formulse used in actual practice to deter- 
mine the size of wire, speed, etc. ? 

Ans. These formulae are of value principally in check- 
ing up the actual calculations made. 

827. How is an armature actually designed? 

Ans. In actual practice whenever a new dynamo or 
motor is to be constructed it is, so to speak, built up around 
the armature. That is to say, the armature must first be 
designed, and the other parts made to fit around it. 

828. What is the principal consideration to be taken 
into account? 

Am. In order to deliver a certain current, the number 
of poles, etc., being fixed, which is with rare exceptions the 
case, we must use a certain size wire. 

829. Is there no choice whatever in the size of wire 
for a given current? 

Ans. There is some choice. In most cases the heating 
of the wire on the armature determines the size of wire to 
be used; in other cases it is the drop in potential at the 
terminals of the armature that governs. 



124 Steam Engineering 

830. How does the size of wire affect the heating, and 
the Iobb of potential? I 

Ans, Both of these losses, and the troubles occurring? 
from them, are lessened by selecting wires of greater,' 
diameter. 

831. How do you proceed to calculate the necessary size 
of wire? 

Ans. The number of wires, and the dimensions of the 
armature for any given purpose can be found by trial cal- 
culations only. By this we mean that, unless we are very 
lucky, we shall have to make a number of calculations,! 
using, perhaps, different dimensions and wires before wef 
get the result that suits us best. 

832. Give an example. 

Ans. As an example let us take an armature 8 inches 
in diameter and 8 inches in length and see what it will 
do for us. Such an armature has a cross-section of 64 sq. 
inches and, assuming a flux of 30,000 lines of force peri 
square inch, we have a total flux of 1,920,000 lines through; 
the armature. We first find how often one wire must cuti 
this number of lines of force to generate, say, 110 volts. 
To do this we first divide 110X100,000,000 (which is thej 
total number of lines to be cut per second) by the total! 
flux, 1,920,000, and obtain as the result 5728. Next, to 
get the necessary number of wires to be placed upon the' 
armature, we must divide this quotient (5728) by tbq' 
number of revolutions the armature makes per second. If 
our armature revolves at the rate of twenty revolutions peij 
second (1,200 per minute) we shall need one-twentieth' 
of 5,728 wires placed upon it. This amounts to 286. As 
our armature, 8 inches in diameter, has a circumference of 
25.12 inches, this gives us a wire running about 11 pei^ 



Wire Used 125 

inch. If there is to be but one layer, this gives a number 
12 wire. As the two sides of the armature are in parallel 
we have a capacity of 2 times 14.31 amperes according to 
Table 50. If we decide to use two layers, we can take a 
No. 6 wire, 5.5 per inch, and obtain a capacity of 56.55 
amperes. It may be stated in explanation of the calcula- 
tions here made that each wire in the cour&o of one revolu- 
tion of the armature cuts the total flux two times; but a? 
the two halves of the armature are in parallel, each side 
must produce the full voltage by itself. 

833. How much radiating surface is usually allowed per 
watt of energy used up ? 

Aiis. That depends very much on the work for which 
the armature is intended. If it is for a railway motor, 
which is entirely enclosed, and almost constantly in use, it 
is much more than, for instance, an elevator in a private 
residence where there is but very little use, and only at long 
intervals, so that the armature has time to cool off between 
one run and another. Table 50 is based upon the require- 
ment that there shall be three square inches of radiating 
surface for each watt of energy expended in the coils. 

834. What radiating surface is allowed for each watt 
expended in the case of an armature ? 

Ans. This amount varies in different machines, being 
as low as 1 square inch per watt, and as high as three aquare 
inches per watt. About 1.75 square inches per watt ex- 
pended can be considered as a fair average for armatures 
and about 3 inches per watt expended for field coils. 

835. How is the table referred to (Table 50) made tip? 
Ans. This table is figured from the formula, 

3XK 



= 4 



126 8te ing 

R 3 being the radiating surface, and B the resistance of a 
unit of length of the wire under consideration. This form- 
u!a gives the current allowed where the wire is wound in 
one layer. As we add more layers we must, with each sue- 
eeasive layer, reduce the current, so that the square of the 
current multiplied by the resistance (which equals the 
watts) shall remain always the same, because increasing 
the df f the winding does not affect the radiating sur- 

face of the coil. 

■5. The table gives the carrying capacity only to a 
depth of sis layers ; how is the carrying capacity of a 
greater number of layers to be found? 

Ans. To to Table 50 and select from 

le number pertaining to the wire in 
question. This number rep - ts the square of the cur- 
rent permissible with one layer of wire. Divide this num- 
ber by th • number of layers it is intended to use, and extract 
the square root of the mu so found. The result will be ! 

the car^ apacity of the wire in question, wound to a 

depth of that number of layers. As a general guide we may 
bear in mind that, as we multiply the number of layers by 
4. 16, 64, 256. we. each time, decrease by one-half the ; 
carrying capacity of I re. From this we can see t 

the capacity of the wires after a certain number of layers 
have been considered, decreases very slowly, though very 
fast with the first few layers. 

837. Is there need of very great accuracy in these 
nlations? 

Am. Great accuracy is n •:■: nee in these calcula- 
tions. We can always >nr armature a little by 
adding a few punching?, tential be insufficient, 
aad we can always •■ I and sti o of field con- 



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Armature Winding 129 

siderably. Adding to any of these would tend to increase 
the B. M. F. of the armature, but not its capacity in 
amperes. 

838. If the capacity of the armature is not sufficient, 
how do we proceed ? 

Ans. Take the next larger wire, or such a wire as will 
give the desired capacity, and from the diameter of this 
wire figure out a new armature. By using the same num- 
ber of wires of a larger diameter, a greater cross-section of 
armature is obtained. 

839. Do these considerations apply equally well, 
whether an armature is slotted, or not? 

Ans. The only difference is that with a slotted arma- 
ture it is necessary to take into consideration the length of 
the winding space in the slots only, not the total circum- 
ference of the armature. There is also considerable loss of 
flux through the teeth of the armature so that the flux must 
be assumed less. A great flux is obtainable, however, with 
the same field winding, as the magnetic circuit of a dynamo 
with a slotted armature has less resistance. 

840. How do you proceed in the case of a slotted arma- 
ture? 

Ans. If we have an armature provided with slots of a 
fixed size we can but arrange to accommodate ourselves to 
it as best we may. It may be that the slots are of such size 
that the wire we have selected through our calculation will 
not fill out the slot well, and we must, therefore, try some 
other size wire. In this case it will be preferable to select 
a larger size wire if practicable. This had best be tried by 
actual experiment. As the wire often will not fill out the 
slot quite fully, calculations are not exactly reliable. Any 
deficiency can, of course, be made up by filling in with insu- 



130 Steam Engineering 

lation. The number of wires per slot is found by dividing 
the total number of wires by the number of slots. 

841. How can the size of a slot capable of holding a 
certain number of wires be determined? 

Ans. The approximate depth of the slot can be obtained 
by multiplying the diameter of the wire to be used by .86 
and this by the number of layers placed over each other. 
The result will be exact if the wires lie as shown in Figure 
512. The width of the slot can be found by multiplying the 
diameter of the wire by the number of turns per layer. It 
will be seen from the figure that each alternate layer will 
contain one turn less than the first. 

842. Can slots be proportioned so that they will accom- 
modate any number of wires ? 

Ans. The slots must be proportioned to the number 
of wires to be used, and the number of wires per slot must 
be carefully considered. If the number of turns per slot 
are few, the wires should be placed as shown in Figure 513. 
If there are many, according to Figure 512. Which of these 
two methods is to be used will have a bearing on the num- 
ber of wires per slot. The total number must be a multiple 
of the number of layers. 

£43. After we have selected our wire, and determined 
the number of wires to be used, can we form some idea of 
what the losses in the armature will be? 

Ans. We can easily figure the approximate loss of volt- 
age in the armature from the size of wire to be used. To 
do this we first find from Table 50 the resistance per foot of 
the wire in question, and then measure the length of wire 
in one coil and multiply the resistance by the number of 
feet. If we have a bi-polar armature wa again multiply 
this by half the number of coils (the two sides being in 
parallel). Since the loss in voltage is equal to the amperes 



Armature Winding 131 

multiplied by the resistance, we need but to multiply the 
resistance so found by half the total current to find the 
loss in voltage that will occur. This loss is, of course, in 
direct proportion to the current. This loss is not of much 
importance in ring armatures, or in drum armatures either, 
when they are working with small currents, or on constant 
current work such as arc lighting; but with heavy, and 
variable currents it is a very important matter, and the 
lower the losses can be kept, the better. 

844. Are there any special considerations to be borne 
in mind while winding the different coils ? 

Arts. It is quite important to see that each coil contains 
the same number of turns, and that these fill out the same 
relative space. 

845. Why is this so important? 

Ans. We have already seen that the two halves of the 
armature are generating in parallel, that is, the currents 
from the two sides meet at the positive brush and flow out 
to the line, and return by the negative side to the armature. 
If now there are fewer turns of wire on one side than on 
the other, or if there is one weak coil in the armature, one 
side or the other will always be generating a greater E. M. F. 
than the other and consequently current from the high pres- 
sure side will flow through the winding of the low side. 
To see this more clearly refer to Figure 514. On the arma- 
ture there shown, there are 16 coils. If this armature is to 
generate 40 volts, each coil will be called upon to produce 5 
volts. Now suppose one of the coils to be cut out of the 
circuit entirely. It is clear that at all times except when 
the dead coil is at the neutral points, there are 8 coils gen- 
erating on one side against 7 on the other; i. e., 40 volts 
against 35. In order to find the current that would flow in 
such an armature while on open circuit, subtract the low 



132 Steam Engineering 

voltage from the high, which leaves an active voltage of 5. 
If the resistance of the armature were .1 ohm a current of 

amperes will be circulating a great part of the time. 

SAG. Why would this not be a constant current? 

Arts. For the reason that this current would be con- 
stantly changing in direction, because the strong side of the 
armature would be first on one side, and then on the other, 
of the fields. On open circuit a perfect armature would 
generate no current whatever ; with an armature as de- 
scribed the current mentioned would always be flon 
toward the coil which is cut dead. 

The current would be c 
ing the time the dead coil is short circuited by a bru- 
would be balanced by another coil under the opposite brush 
whicl moment is uently during 

that time the armature would not be generating at all. 

847. How would this inequality of generation man: 
If if the dynamo were generating curren 

Arts. " If the dynamo were sreneratincr current on- 

d would greatly reduce its capaei r e current flows 

in obedience to the pi 
variable the curr uld of cou be variable. 

:fferences in pc ij n different parts 

of an armature caused by any other conditions in the ar- 
mature : 

Am differences aro na- 

tion of the wires of different being e 

E. M. F. generated I coil varies with its distance 

from the center of the armature. It can readilv be seen 
that the farther a wire is from the center, the greater will 
be the area enclosed and therefore the greater the number 
of lines of force cut by it. 



Armature Winding 133 

849. What other cause is there for inequality of genera- 
tion? 

Arts. Another cause for inequality of generation be* 
tween different coils lies in a difference of resistance. 

850. Does this affect the generation on open circuit? 

Arts. It does not. We have already seen that the loss 
in potential in any circuit is proportional to the current 
flowing, multiplied by resistance of the circuit in which it 
flows. Therefore the drop in potential in any coil is in 
proportion to the current being taken from it. If one coil 
therefore has a much higher resistance than the others its 
potential will fall much more, and the side of the armature 
on which it happens to be will be of lower E. M. F. than 
the other, and there will be the same tendency to a vacillat- 
ing current as in the case of coils of uneven number of 
turns. The variations will, however, not be near so great, 
for an excessive current flow from the strong side will re- 
duce the pressure on that side, and the checking of the cur- 
rent on the low side will raise the pressure there, so that a 
balance will be obtained without any great current flow. 
The main danger of introducing inequality in the resistance 
of the winding lies in the winding of the inside of the coil 
with Gramme ring armatures. The space for the winding 
at this point is necessarily of a different shape than that 
on the outside, and there are also the spokes of the arma- 
ture to contend with. 

851. How many methods of armature winding are in 
general use ? 

Arts. The methods of armature winding are very numer- 
ous. For the present we shall confine ourselves to the 
methods used with hand winding on cylinder armatures. 

852. WTiich is the most simple of these windings? 



134 



Steam Engineering 



Ans. The simplest one of these windings is that shown 
in Figure 534, and we shall take this one for the purpose ' 
of demonstration. It will be noticed that in this figure there 
are 12 slots in the armature and 6 commutator sections, ^ 
indicated by the wires twisted together. 

853. Is it necessary that this proportion of slots and 
armature coils exist? 




Fig. 534 

Ans. It is not; in fact it is not at all desirable that this 
proportion should exist, but this proportion is very con- 
venient for winding, as we shall see. 

Begin winding by selecting two of the slots located 
opposite each other, as shown in the figure, and starting 
at 1 wind into those slots as many turns of wire as has been 
determined there should be and bring the last end of the 



Armature Winding 135 

coil to the commutator section next the one from which we 
started. 

854. Should this be to the one in front of, or behind 
the section from which the winding started ? 

Ans. This is immaterial. In actual practice there 
should not be any commutator sections in place while wind- 
ing. They would be very much in the way. Instead, tie the 
two ends of the coil together and properly mark the be- 
ginning and end. 

855. Are all coils wound in the same way? 

Ans. They are; but in this case we must skip one slot 
at each subsequent coil, in order to make them come out 
right in the end. That is to say, if the first coil is wound 
into 1, 1, the second must be wound into 2, 2, the third 
into 3, 3, etc. 

856. Why is this? 

Ans. As each coil fills out two slots, we have with the 
third coil finished half of the armature. If we were to wind 
the slots in consecutive order, the connections for the com- 
mutator would all come on one side, and we could do noth- 
ing with the armature. As we now continue in the order 
we have started we finally complete the entire winding and 
have the beginning and end of one coil opposite each com- 
mutator section. We can now fasten the beginning of the 
first coil to its proper commutator section, and the end of 
it to the next one. It will be immaterial whether this be to 
the section ahead, or behind the starting section, but, which- 
ever way we start, we must be sure to continue in the 
same way. 

857. This being the most simple method of armature 
winding, why are not all armatures wound in this way? 

Ans. The great objection to an armature wound in this 
way is that the coils become too large. 



136 Steam Engineering 

858. Why are large coils objectionable? 

Arts, In order to understand why large coils are objec- 
tionable we refer to the commutator shown at the right of 
Figure 534. Here a brush is shown bridging two commu- 
tator sections and short circuiting the coil connected to 
them. The coil indicated by the black line is the same one 
shown in the slots 1, 1, and the connections are identical. 
It can readily be seen that all of the coils will in turn 
become short circuited in the same way in the course of 
every revolution of the armature. 

Now in the first place assume that the coil when thus 
short circuited is in an entirely dead part of the field. 
When a brush short circuits such a coil it takes all the 
current away from it. WTien the brush leaves the forward 
section of the commutator this short circuit must be broken, 
and current must be again established through the coil. 
As every coil possesses some inductance (which acts for an 
instant like a very high resistance), there is a tendency for 
the current in that half of the armature to jump across the 
insulation between the commutator sections, rather than 
pass through the coil. If this occurs there is destructive 
sparking. The greater the number of turns of wire in any 
coil, the greater will be the likelihood of this taking place. 

859. Is this the main reason why the coils on an arma- 
ture should be made up of few turns of wire ? 

Arts. It is not. The most important reason for this is 
the following : If the coil is not in an entirely "dead" pari; 
of the field there is always some current generated in it 
during the time the brush is in the position discussed above. 
This current circulates in the coil during the time the 
brush holds it on short circuit, without appearing- in the 
outer circuit, and is therefore a dead loss. It furthermore 



A r mature Winding 



137 



fends to heat the coils. Because two of the coils are nearly 
always on short circuit in this way, the loss and the heating 
are considerable when the coils are large. When these cur- 
rents are broken by the commutator section sliding from 
under the brush, they also make themselves evident by 
severe sparking, if the coils are large. 




Fig. 535 

860. Are there any more reasons why large coils are 
objectionable ? 

Ans. Another reason why large coils in an armature 
are objectionable can best be understood by reference to 
Fig. 535. A simple dynamo such as is depicted in this 
figure delivers a current graphically illustrated by Fig. 536. 
It will be seen that this is really an intermittent current. 
This is because the dynamo has but one coil, and while 



138 Steam Engineering 

this is at the neutral points, nothing is being generated. 
The current therefore fluctuates from to its maximum. 
If we add one more coil the current line becomes as shown 
in Fig. 537, and the greater the number of coils the smaller 
becomes the percentage of non-generating coils, and the 
nearer does the current line approach a straight line show- 
ing a steady value. 

861. Why cannot small coils be wound in the manner 
shown in Fig. 534. 

Ans. It is desirable to make the coils as small as pos- 
sible. The ideal coil would consist of only one turn. Xow 

AAAAAAAA 

Fig. 536 




Fig. 537 

as long as we wind only one coil into one slot we shall 
have the coils needlessly large. The number of coils is 
limited by the number of commutator sections, and unless 
we wind two coils into each slot (as we can see from Fig. 
534) we can Lave but half as many commutator sections 
a* there are slots. In order to get a small coil it is there- 
fore necessary to get two coils into each slot. 

862. Can this be done in more than one way? 

Arts. This can be done according to any of the plans 
shown in Fig. 538. In this figure the black and white 
circles respectively represent the wires of the two different 
f oils wound into the same slot. 



Armature Winding 139 

We have already seen under ring armatures, that wires 
of different coils should all he of the same distance from 
the center of the armature, so as to cut the same number 
of lines; it follows, therefore, that the plan showing one 
coil wound over the other should not be used where it can 
be avoided. 

863. How do you manage to place two coils in one slot? 

Ans. In order to understand exactly how this is done 
let us consult Fig. 539. This figure is a duplicate of Fig. 
534 with the exception that now we have as many com- 
mutator sections as there are slots in the armature. The 




v&**^*%®2m»®$. 



Fig. 538 

black circles represent the wires of one set of coils, and the 
light those of the other. 

The simplest method of winding two coils into one slot 
is, first to wind one coil complete, filling half the slot, then 
turn the armature half way round and wind the second 
coil over the first. As this, however, gives two coils of dif- 
ferent lengths and resistance, and also cutting a different 
number of lines of force, such a winding is seldom used. 
A better way is the following: Cut two wires of sufficient 
length so that each will make one coil, place the armature 
upon two crossbars of convenient height so that it can be 



140 



Steam Engineering 



easily turned over when required. Mark all of the slots 
with appropriate numbers according to the plan of wiring 
selected, so there may be no confusion when the work is 
started. A very good plan is shown in Pig. 534. This 
plan gives the smallest head of any because there are al- 
ways two coils running parallel to each other across the 
ends of the armature. Thus we have three lavers of coils 




Fig. 539 

crossing over each other, while with any of the others 
we should have six. But in order to get the advantage of 
this smaller head, we cannot wind the coils in the order 
given in the explanation of this winding. It becomes neces- 
sary to wind completely, at the same time, the two coils 
that are running parallel with each other across the ends. 
To do this requires more experience and forethought, than 
the way previously described. 



Armature Winding 141 

Begin the winding with the coil marked 1, and make 
one complete turn and fasten the two ends of the wire to- 
gether temporarily if more turns are to follow, or fas- 
ten each to its proper place on the commutator, if there 
is to be but one turn. Now turn the armature half way 
round and wind the other wire in the same way. If there 
are to be more turns, continue to wind the second turn. 
After this is finished turn the armature back to its original 
position and wind the first wire again. Eepeat in this 
manner until the desired number of turns in both coils have 
been obtained. By reference to Fig. 539 we note that the 
windings do not skip slots as in Fig. 534. This is easily 
explained when it is noticed that each slot contains two 
conductors and that at each step we skip one conductor as 
before. 

It is not necessary in actual practice to turn the arma- 
ture around as above suggested. This was suggested merely 
as a beginning to make the principle more plain. The 
same result can readily be obtained if the armature is left 
stationary. The windings need merely to be so arranged 
that they will come right for connection to the commutator 
as shown in the cut. 

It is well enough to use care that all of the coils are wound 
in the same direction, but it will not materially affect the 
operation, if one part of the coils are wound left hand, and 
the others right hand. The essential point is to see that 
they are so connected that the magnetism resulting from a 
current flow through the coil will be the same in all. If 
it is different in one coil from the others it can easily be 
rectified by simply changing the end connections of the 
coil in question. 

864. Are all armatures hand wound ? 



142 



Steam Engineering 



Ans. Hand winding is customary with the smaller 
drum, and ring armatures only. It is the only method 
that can be used with ring armatures, and also with drum 
armatures where the wire is to encircle the whole armature. 
The larger dynamos are now made mostly multipolar, and 
in these the coils do not return at nearly, or wholly, diam- 
etrically opposite points as they do in those machines we 
have so far had under consideration. With multipolar ma- 
chines the armature is divided into as many sections as 
there are poles. While it is possible to work any regularly 




Fig. 540 



wound drum, or ring armature in connection with manv 
poles, it is not customary to do so. In general the coil 
wound on a multipolar armature has its return winding 
spaced about as far from the first turn, as it is from the 
center of one pole piece to the center of the next one. 

865. How does this affect the winding? 

Ans. This gives us a winding of much lower resistance 
than could otherwise be obtained, and the magnetic circuit 
is also much better. Furthermore, it makes possible the 
use of so-called "former coils." 



Armature Winding 



143 



866. What is a former coil ? 

Ans. A former coil is one that is wound upon a former, 
i. e., one that is wound complete before it is placed upon the 
armature. 

867. How are such coils made up ? 

Ans. Figs. 540 and 541 show two styles of former coils, 
and the manner in which they are wound. In Fig. 540 the 
black circles represent strong pins fastened into a piece of 




Fig. 541 
plank, or other suitable material. The wire is wound 
around these pins as indicated in the figure, as many turns 
being taken as it has been decided to allow for each coil. 
When the coil is thus completely wound it is taken from 
the pins, and the lower ends placed in a suitable clamp, as 
indicated by the broken line in the lower center of the 
figure. After this clamp is fastened onto the coil the two 
halves of the coil are spread apart, one being pulled to- 
ward the operator and the other pushed away from him at 



144 Steam Engineering 

right angles to the clamp. In this way the coil is made to 
assume the shape illustrated in Fig. 542. Before winding 
a coil in this manner it is of course necessary to know ex- 
actly what length it must be, and a pattern coil must there- 
fore first of all be prepared, from which the spacing of the 
pins can be taken, so that the completed coil will fit into 
the slots for which it is intended. 

868. How are such coils placed upon the armature? 

Arts. Begin placing the coils at any convenient slot, and 
lay them in, as indicated in Fig. 542. It is necessary to 
mark the beginning, and end of each coil, so that there 
may be no wrong connection when the wires are finally 
connected to the commutator. 




Fig. 542 



Before placing the coils the slots must of course be in- 
sulated as explained previously. We now continue to lay 
in coils until the whole armature is full, but when nearly 
full, the forward ends of the coils we are placing require 
to be brought under the first coils put in place. To do 
this it is merely necessary to raise up the first six coils, 
(in this case) and place the forward ends of the last six 
under them in the regular order. 

869. By what name is this winding known? 

Arts. This is known as the "evolute" winding. It will 
be noticed that when this winding is completed, the wires 
of the outer portion entirely conceal those of the inner, and 
thus give this style of winding its characteristic appearance. 



Armature Winding 145 

870. What other manner of winding multipolar arma- 
tures is there? 

Ans. Another method of forming coils is illustrated in 
big. 541. In this case the coil is first wound around two 
'ipins, as shown at bottom of the figure. The ends are then 
j placed in clamps, as indicated by the dotted lines at bot- 
tom and shaded lines in the center of the figure. After 
' these clamps are fastened, the coil is turned one-fourth 
I around, and the wires spread over the four pins, as indi- 
i cated in the figure. 

871. How is this coil placed upon the armature? 




Fig. 543 

Ans. The coil formed in the manner above assumes the 
shape shown in side view in Fig. 543 and is placed upon 
the armature as there indicated, the manner of placing 
being the same as that of the previous coil. 

872. What name is given to this style of winding? 
Ans. This is termed a "barrel" winding and its charac- 
teristic appearance can be seen from the figure. 

873. Is it necessary to carry out the same kind of wind- 
ing on both sides of an armature? 

Ans. There is nothing to prevent one from using one 
of these windings on one side of the armature, and the 
other on the opposite side. They cannot, however, be com- 
bined on the same side. The windings of large machines 
very often are made up of bars of copper made of special 



146 



Steam Engineering 



ST a ™ ^ ^ ° ften arranged as sho ™ * Kg, 
544 and 545 Sometimes such bars are bare and laid i$ 

the slots with insulation loose on the sides and bottom and 

between the different bars of a slot. Such winding Tj£ 

held m place by pieces of wood inserted into the slots 3 

admf o C f tV Ivf 3 ' the Sl ° tS b6mg ""** P-P^ « 
admit of this Where no such provision has been made tbj 

wnes are held in place by the usual binding wires. \ 

874. Is there any difference between the armature o*\- 

motors and dynamos ? 




ft 



Fig. 544 



MOTOR ARJf ATCRES. 

4w. Theoretically there is no difference between the 
amature of a dynamo and motor. In fact, many machines 
are placed in conditions in which their functions change 
perhaps a hundred times per day, *rom that of generator' 
to that of motor. 

875. Are there any special provisions necessary to make 
them operate thus ? 

Ans. No. This change takes place automatically, and 
the operation is so smooth that the observer will have no 
idea m which capacity the machine may be operating from 
moment to moment. It is also no unusual thing for a 
dynamo working in parallel with other generators to be- 



Armature Winding 



147 



come reversed, and instead of delivering current to the 
line, it will be drawing from it and running as a motor. 

876. What should one principally have in view in the 
design of a motor armature ? 

Ans. Motor armatures must be designed to produce a 
certain counter E. M. F. just as dynamo armatures are 
designed to produce E. M. F. In the case of a dynamo the 
power is measured by the product of the E. M. F. and the 
current, so in the motor the power is proportional to the 
product of the counter E. M. F. and the current. 




Fig. 545 

877. How do you proceed to calculate the winding for 
a motor armature? 

Ans. In the same way as with a dynamo except that 
the E. M. F. should not be figured as high. The current 

V-v 

passing through a D. C. motor equals , where V is the 

volume of the line that supplies it; v the counter E. M. F. 
of the armature, and E its resistance. It is apparent that 
in order to get more power out of a given motor, its coun- 
ter E. M. F. must be reduced in order that a greater cur- 
rent can flow. 

878. How is this brought about? 



148 Steam Engineering 

Ans. With a motor in operation this counter E. M. F. 
is reduced when the speed reduces, on account of a heavier 
load. More current is thus allowed to flow until the power, 
of the motor becomes equal to the work required of it, but' 
if the load exceeds the capacity of the motor it will take 
too much current, and burn out the armature. If a motor 
is to be designed to operate at a certain speed, all of these 
facts must be taken into consideration, and the wires so 
selected that when running at the required speed, the neces- 
sary counter E. M. F. will be generated. 

For illustration, take the same armature that was con- 1 
sidered in the previous section. In this case a JsTo. 12 wire 
was required. This gave 11 turns per inch, and its car-' 
Tying capacity was 14.3 amperes. The dimensions of the 
armature were 8"x8", requiring about 770 feet of wire. 
With this quantity of No. 1.2 the resistance is 1.39 ohms. 

Only one-half of this, however, is on one side, and only 
14.3 amperes pass on one side, so that the total E. M. F. 
to drive this current through the armature is 14.3 X .697, 
which is 9.96. In order that this motor may allow the 14.3 
amperes to pass, its counter E. M. F. must fall to 9.96 
volts less than the E. M. F. of the line. If this is 110, the 
speed must slack off about 9 per cent in order that the 
motor may develop its full power. 

It is easily seen from this that, in order that the motor 
may operate at a fairly constant speed, the resistance of the 
armature should be made as low as possible. In practice it 
is generally made so low that a reduction of 1 per cent in 
speed wll bring about the required lowering of counter 
E. M. F. to cause the proper current to flow. 

879. How do armature troubles manifest themselves ? 

Ans. Either by excessive sparking at the commutator, 
or by abnormal heating of the armature. 



Armature Troubles 



149 



880. What are the causes of such troubles ? 

Arts. They may result from any one of the following 
causes: There may be a wrong connection of one, or more 
of the coils. Some of the coils may be grounded. There 
may be an open circuit. There may be a short circuit. 
The brushes may be improperly set. The brushes may not 
make sufficient contact with the commutator. The com- 
mutator may be rough or worn. The fields may be of 
uneven strength. 




Fig. 546 

881. How can a wrong connection of the coils be tested 
for? 

Arts. In order to see how this test can be made let us 
consider Fig. 546 for a moment. This figure shows the 
wiring of an armature connected to the commutator seg- 
ments exactly as it would be if it were taken off, and the 
coils separated without detaching from the commutator, in- 
stead of being placed in an orderly manner upon the core 
of the armature. In other words, the connections are ex- 
actly as in an armature. If we should now take the two 



150 Steam Engineering 

wires of some supply of current capable of delivering a 
few amperes, and connect these two wires to two adjacent 
commutator segments, as shown at a, and h, it is clear that 
current would flow through the coil connected between 
these two sections, and also through the other coils. The 
current has two paths: one through the single coil, the 
other through the remaining seven coils in series. 

The current in the two coils flows in opposite directions, 
with the result that a field of force is set up in the vicinity 
of the single coil. A suitable galvanometer placed at this 
point will be deflected in a certain direction. By revolving i 
the armature and applying the test to each succeeding pair 
of commutator sections, a number of deflections of the I 
needle will be obtained. 

If all the coils are correctly connected these deflections 
will all be in the same direction. If one of the coils is con- 
nected wrong, a different deflection will be obtained. If 
one of the coils has been wound on in the wrong direction, 
it is not necessary to rewind it ; the connections can simply 
be reversed. 

882. What is meant by a "ground" ? 

Ans. An electrical connection between some current 
carrying part of the armature, and the metal armature 
frame. A "ground" is often caused by the insulating cov- 
ering of the wire breaking down, thus allowing the wire to 
come in contact with the iron core. 

883. How do you test for this condition ? 

Ans. The simplest method of testing for a ground con- 
sists in taking a lamp or voltmeter and connecting it as 
shown in Fig. 546. Place one of the wires in contact with 
the iron core, and the other in contact with the wire on 
the armature. If the lamp lights, there is a connection be- 
tween the wire and the core, and this should be removed. 



Armature Troubles 151 

884. How is an open circuit located ? 

Ans. Eef erring to Fig. 546, connect the commutator 
as shown by the horizontal lines c. d. to some source of 
supply. A rheostat is needed to adjust the current strength 
until a suitable deflection of the needle is obtained between 
adjacent commutator segments. Now, take two wires of 
the voltmeter and test the voltage between the various ad- 
jacent commutator segments. A reading will be obtained 
between each two segments on one side of the commutator, 
but on the side which contains the open coil no reading 
will be obtained until connection is made between the two 
segments to which the open coil is connected. At this 
point the voltmeter will show practically the full voltage of 
the supply current. 

885. How do you locate a short circuit? 

Ans. If the short circuit has come on while the arma- 
ture was in use, it will locate itself by a burned out coil. 
To test a new armature for short circuits we can proceed 
in the same way as for open circuit, the only difference 
being that, when we come to the short-circuited coil, we 
shall obtain either none, or at least a reduced deflection. 

886. What effect does an improper location of the 
brushes have? 

Ans. An improper location of the brushes will mani- 
fest itself by a more or less severe sparking. If the brushes 
are of the right dimensions the trouble can be remedied 
by simply shifting them to the proper location, which is that 
of least sparking. Brushes should be of such length, and 
set at such an angle, that they come in contact with diamet- 
rically opposite points on the commutator, with all bi-polar 
machines. 

887. How must the brushes be set in connection with 
multipolar machines? 



152 Steam Engineering 



Ans. This depends on the manner in which the armature 
is wound. With a lap winding there are as many brushes 
as there are pole pieces, and they must be equally spaced 
around the periphery of the commutator. Provision must 
also be made so that they can be shifted to the point of least 
sparking. In wave wound armatures there may be only 
two brushes, these being so spaced that they are separated |i 
by an angle equal to the angle of separation of two ad- 
jacent pole pieces ; for instance, with a four-pole field they 
would be separated by an angle of 90°. 

888. Is much shifting of the brushes necessary? 

Ans. This depends very much on the design of the ma- 
chine. With some of the older machines constant shifting 
of the brushes is required with changes in the load, but with 
the newer, and better machines this is reduced to a mini- 
mum. 

889. What is the ordinary size of a carbon brush? 
Ans. It should be of such size that not more than 25 

to 40 amperes per square inch of carbon are ever required 
to flow through it. 

890. How does inequality in field strength affect an ar- 
mature ? 

Ans. Wherever this exists there will be more lines of 
force cut by the armature on one side than on the other, 
thus causing a higher potential to be generated on one side 
than on the other. The brushes will have to be set uneven 
distances apart around the commutator, and useless cur- 
rents will be set up in the armature windings, which will 
not only cause a loss of power, but which will tend to over- 
heat the armature. 



Transformers 



891. What is the function of a transformer ? 

Arts, To transform the current from a higher, to a lower 
voltage, or vice-versa. 

892. What principles govern the action of a trans- 
former ? 

Arts. The principles of electro-magnetic induction. 

893. What is a step up transformer? 
Ans. A transformer that raises the voltage. 

894. What is a step down transformer? 
Ans. One that lowers the voltage. 

895. How are transformers cooled? 

Ans. Small sizes by surface radiation. Larger sizes by 
oil ; also by air blast. Some of the smaller sizes are cooled 
by water circulating through surrounding coils. 

896. How is direct current transformed from one volt- 
age to another ? 

Ans. By means of a machine called a motor-generator. 

897. Describe in brief a motor-generator. 

Ans. It consists usually of a D. C. motor driven by 
current at the voltage of the incoming line. This motor in 
turn drives a D. C. generator that furnishes current at the 
desired voltage. 

898. How is the outgoing voltage regulated? 

Ans. By altering the field strength of the generator. 

899. In case the incoming and outgoing current can bear 
the same ratio to each other constantly, what kind of an 
apparatus is used ? 

Ans. A machine called a dynamotor. 

153 



154 Steam Engineering 

900. Describe the operation of a dynamotor. 
Ans. It is a D. C. motor running on the incoming volt 

ages. On the same armature core is a separate winding 
connected to its own commutator at the other end of the 
armature. One set of field magnets serves for the motor 
winding and the generator or dynamo winding. 

901. Describe in general terms a rotary converter. 

Ans. It combines in a single machine the functions of 
a motor-generator, and a dynamotor. 

902. Why are rotary converters and transformers neces- 
sary? 

Ans. Because it is more economical to transmit alter-' 
nating current at high voltages and transform, or convert 
it to the lower voltage at which it is used. 

903. Give another reason for using rotary converters. 
Ans. For the purpose of transforming alternating cur- 
rent into direct current when direct current is used. 

904. What is the chief point of difference between a 
rotary converter and a direct current generator? 

Ans. The rotary has collector rings connected to certain 
points of the armature winding. 

905. What governs the number of such connections? 
Ans. The number of poles and phases. 

906. Describe the different types of rotaries. 

Am. They are built for single-phase, two-phase, three- 
phase or six-phase. 

907. How many collecting rings has a two-phase con- 
verter ? 

Ans. Four collecting rings. 

908. How many collecting rings has a three-phase con- 
verter ? 

Ans. Three collecting rings. 



Rotary Converters 155 

909. When alternating current is transmitted at high 
pressure, what means are employed for lowering the po* 

3 tential ? 

A ns. Transformers. 

910. When the incoming current is direct and the out- 
going current alternating, how is the voltage raised ? 

Ans. By step up transformers. 

911. Describe the winding of a rotary converter. 

Ans. It is usually shunt wound, or compound wound, 
although sometimes separately excited. 

912. How are rotaries in railway service usually wound ? 
Ans. Compound, owing to variations in the load. 

913. What advantage is gained by this method of wind- 
ing? 

Ans. It tends to maintain the D. C. voltage constant. 

914. Upon what does the ratio between the A. C. and 
D. C. voltages of a rotary depend? 

Ans. Upon the number of phases, the lead given the 
D. 0. brushes, the wave form of its alternating current, 
and upon the field excitation. 

915. Does the armature drop affect this ratio to any 
extent ? 

Ans. It does by decreasing it slightly when running 
A. C. to D. C. and increasing it when running D. C. to 
A. C. 

916. What are the ratios of conversion approximately? 
Ans. Single-phase 71 

Two-phase 71 

Three-phase 61 

Six-phase 71 or .61 

917. Give an example illustrating above. 



156 Steam Engineering 

Ans. If D. C. voltage is 550 volts, the A. C, if two- 
phase will be 500X.n=390 volts, or if three-phase it will 
be 550X61=335 volts. 

918. What precautions should be observed in the erec- 
tion of a rotary converter? 

Ans. First — It should be protected from moisture. Sec- 
ond — It should be protected from dust or dirt. Third — It 
should be in a well ventilated room and kept as cool as 
possible. 

919. Should the frame of the machine be insulated? 

Ans. Generally speaking the strain on the winding in- 
sulation will be decreased, and danger to attendant increased 
by insulating the frame. 

920. If a rotary has been exposed to dampness how may 
it be dried out? 

Ans. Short circuit the field and apply to the col- 
lecting rings about 10 per cent of normal A. C. voltage. 
During this application the D. C. brashes must be 
raised and the rotary at standstill. 

921. What method should be pursued in caring for the 
commutator ? 

Ans. Wipe it off with a piece of canvas — never use waste. 
Lubricate it with a very small quantity of vaseline, or oil 
applied with a piece of cloth. See that none of the segments 
is at all loose. 

If it gets out of true turn it down. 

922. If a commutator gets hot while carrying only a 
normal load what should be done? 

Ans. Heating under such conditions is an indication 
that the commutator is worn out, and should be replaced 
by a new one. 

923. Give some of the causes of sparking at the brushes. 



The Commutator 157 

Ans. Brashes ma}' not have proper lead. 
Brushes may not fit commutator. 
Brushes may be burned on end. 
Commutator surface may be rough. 

924. What is meant by a rotary bucking? 

Ans. When arcing occurs between two adjacent brush 
holder arms, thus short circuiting the machine. 

925. Fame a few of the principal causes of bucking. 
Arts. Eough or dirty commutator. 

Excessive voltage. 
Fluctuations in the voltage. 

926. What is an oscillator, and what is its function? 

Ans. An oscillator is a device operated either magnet- 
ically, or by mechanical means, and its function is to pro- 
duce a slight, periodic movement of the armature shaft 
endwise. 

927. Why is this endwise movement of the shaft neces- 
sary? 

Ans. In order to prevent the wearing of grooves in the 
commutator. 

928. What is meant by the hunting of a rotary con- 
verter ? 

Ans. It is a slight change of the speed of the armature, 

929. What is the cause of hunting? 

Ans. Irregularities in the speed of the generator deliv- 
ering current to the rotary, thus causing a slight difference 
in the relative positions of the armature of the two machines, 
resulting in a change in the phase positions of the generator 
E. M. F. and the counter E. M. F. of the converter. 

930. What are the usual methods of starting rotary con* 
verters ? 

Ans. First — By a separate A. C. starting motor. 



153 Steam Engineering 

Second — By applying direct current to the commutator. 
This starts the converter as a shunt motor. 

Third — By applying alternating current directly to the 
collector rings. This starts the converter as an induction 
motor. 

^31. What is meant by synchronizing a rotary converter ? 

Arts. Bringing it to the same frequency, the same phase, 
and the same voltage as the generator from which it is 
receiving current. 

932. What method is employed to determine when the 
machines are in synchronism ? 

Ans. There are several methods, the most common one 
being by means of incandescent lamps connected in series 
with the two machines. 

933. What is a synchroscope ? 

Ans. It is an instrument for determining when electrical 
machines are in synchronism. 

934. What is an automatic synchronizer ? 

An*. It is a. device that will automatically synchronize 
two electrical machines: also connect a synchronized ma- 
chine with the main by means of an electrically operated 
switch. 

934a. Name two important points to be looked after 
before starting a rotary converter. 

Ans. First — See that both the A. C. and D. C. brushes 
are properly adjusted and that every thing is clear about 
the converter. Second — See that the switches on board are 
open on both the A. C. and D. C. sides, and that the resist- 
ance of the rheostat is all cut in the field circuit. 



Switch Board 



935. How are switchboards made up? 

Ans. They are built up of panels of slate or marble sup- 
ported by frames of angle iron. 

936. How are the different panels designated? 

Arts. Some are for motor control, others for djmamo 
running, others for operating the outer circuit, and others 
for charging storage batteries. 

937. Is a knowledge of switchboards an important mat- 
ter? 

Ans. It is, and every engineer should especially study 
those in his own station. 

938. What is the regular equipment of a D. C. switch- 
board having a capacity of from 250 to 6,500 amperes? 

Ans. One carbon-break or magnetic blow-out circuit 
breaker with telltale. 

One illuminated dial ammeter with shunt. 

One hand wheel and chain for operating rheoetat. 

One receptacle for voltmeter plug. 

One S. P. S. T. field switch. 

One S. P. S. T. main switch. 

One recording watt-hour meter. 

939. What is meant by the abbreviations S. P. S. T. ? 
Ans. Single Pole Single Throw. 

940. What does D. P. D. T. mean in speaking of switch- 
boards ? 

Ans. Double Pole Double Throw. 

941. What is meant by T. P.? 

159 



160 Steam Engineering 

Ans. Triple pole. It opens every circuit of a three- 
phase system. 

942. Is it good practice to place a main switch at the 
machine ? 

Ans. It is best. 

943. Why? 

Ans. So that the cables from generator to board may 
be cut. off at the generator. 

944. What is an equalizer? 

Ans. It is a cable running along from machine to ma- 
chine, and connecting the junctions of series field and 
brush on all the machines, but does not connect with switch- 
board. 

945. What kind of a break has the field switch? 
Ans. A carbon break. 

946. Describe the action of a field switch. 

Ans. Just before it opens it makes contact with an extra 
clip, and puts a resistance on as a shunt around the field 
coils. 

94?. If this were not done what would be the conse- 
quences ? 

A?is. The fields would act as a spark-coil and the in- 
sulation be damaged. 

948. When if is desired to throw a generator in par- 
allel with other generators already running what is the 
proper method of procedure? 

Ans, First. Close main and equalizer switches near the 
machine. 

Second. Close field switch on panel. 

Third. Close circuit breaker. 

Fourth. Insert potential plug in receptacle and regulate 
voltage. 



Switchboards 161 

Fifth. When proper voltage is obtained close the other 
main switch on panel. 

949. What is meant b}^ voltage? 
Arts. Electric pressure, or potential. 

950. What is a volt? 
Ans. The unit of pressure. 

951. What is a voltmeter? 

Ans. An instrument that indicates the voltage. 

952. Wliat is an ohm? 
Ans. The unit of resistance. 

953. Give a brief definition of Ohm's law ? 

Ans. The electromotive force equals the resistance mul- 
tiplied by current intensity. 

954. What is an ampere? 

Ans. It is the unit of volume, or quantity-time unit for 
measuring the rate of flow of an electric current. 

955. What is a coulomb? 

Ans. It is an ampere-second. A coulomb equals the 
flow of an ampere of current past a given point each second 
of time. 

956. What is an ammeter? 

Ans. An apparatus for measuring current rate. 

957. What is the meaning of the word watt as used 
in electrical work? 

Ans. A watt is the unit of work. It equals volts X am- 
peres. 

958. What is the function of the wattmeter? 
Ans. To record the watt-hours of work. 

959. What is a kilo watt (K. W.) ? 
Ans. 1,000 watts. 

960. Expressed in horse-power, what is one K. W. equal 
to? 



162 Steam Engineering 

Am. 1,000 divided by 746=1^ horse-power. 

961. What is a field rheostat? 

Ans. An apparatus for controlling the current output. 

962. What is the function of a transformer? 

Ans. To transform the current from a higher to a lower 
voltage. 

963. What is meant by synchronism of electric ma- 
chines ? 

Am. When the maximum value of the E. M. F. in 
each machine occurs at exactly the same instant of time, 
the machines are in synchronism. 

964. What is meant by the exciter panel of a switch- 
board ? 

Ans. It is the panel that is equipped with the necessary 
switches, etc., for connecting the small exciter dynamo with 
the other generators in the station. 

965. What is a sub-station? 

Ans. It is the connecting link between the transmission 
line, and the trolley wire or third rail. 

966. When A. C. is generated at the power station, and 
D. C. is used on the line, how is it accomplished? 

Ans. The A. C. is changed to D. C. by rotary converters 
at the sub-station. 

967. What is meant by frequency? 

Ans. The number of times the current reverses per sec- 
ond. 

968. What is the usual frequency for railway motors? 
Ans. 25 is the standard. 

969. What is a frequency changer? 

Ans. A machine which receives current at one frequency 
and delivers it at another frequency. 

9?0. What apparatus is used in an A. C. to D. C. sub- 
station ? 



Switchboards 163 

Ans. Step down transformers, rotary converters, and 
A. C. incoming and D. C. outgoing switchboards. 

971. What is the proper procedure for placing rotary 
converters in service ? 

Ans. After the machine has been started from the A. 
C. ends, and builds up with the proper polarity, first close 
the equalizer switch (on machine) — second, close circuit 
breaker on panel — third, insert potential plug in receptacle 
and regulate voltage — fourth, when the proper voltage is 
obtained, close positive switch (on panel). 

972. What will be the result if the rotary builds up with 
polarity reversed ? 

Ans. The voltmeter will swing back of zero. 

973. How may the polarity be corrected? 

Ans. By means of the four-pole, double-throw field 
break-up reversing switch mounted on the converter. 

974. Describe an oil switch. 

Ans. It is a switch similar in its action to other 
switches, with the exception that its mechanism is im- 
mersed in a small tank of oil. 

975. What advantage is gained thereby? 

Ans. Eeliability of action in opening or closing a cir- 
cuit. 

976. Mention another advantage gained by the use of 
the oil switch and oil circuit breaker. 

Ans. It has made safely possible the transmission and 
use of high-tension currents of electricity. 

977. What is a circuit breaker? 

Ans. It is a switch so designed as to be capable of fre- 
quently opening the circuit carrying its full current with- 
out any damage to itself. 

978. What is a galvanometer? 



164 Steam Engineering 

•Ans. An instrument consisting of a coil of wire car- 
rying the current to be tested, and a magnet, the two be- 
ing arranged so that one can be deflected. 

979. Describe the Thompson type of galvanometer. 

A ns. The coil of wire is stationary, and the light mag- 
netic needle is suspended by a silk thread. 

980. What is a lightning discharge? 

Ans. An equalization of potential between the earth, 
and either clouds, or saturated atmosphere. 

981. What path does the discharge generally follow? 
Ans. The path of least resistance. 

982. What are the general requirements for protection 
of electric stations from lightning? 

Ans. The supplying of paths t«> ground for any charge 
which might accumulate on lines or machinery. 

983. What is the general theory of the multi-gap light- 
ning arrester? 

Ans. When voltage is applied across a series of multi- 
gap cylinders, the voltage distribution is not uniform, but 
is governed by the capacity of the cylinders, both between 
themselves, and also to ground, which results in the con- 
centration of voltage across those gaps nearest the line. 

984. What are the principal elements of a 600 volt 
D. C. aluminum lightning arrester? 

Ans. Tw t o concentric aluminum plates immersed in an 
electrolyte contained in a glass jar, the outside plate of 
each cell being positive, and the inner one negative. 

985. Describe the multigap lightning arrester for A. C. 
Ans. It consists of a series of spark gaps shunted by 

graded resistances, but without series resistance. 

986. Describe briefly the aluminum lightning arrester. 



The Galvanometer 165 

Ans. It consists of two aluminum plates on which has 
been formed a film of hydroxide of aluminum, immersed 
in a suitable electrolyte. 

987. Describe the D'Arsonval galvanometer. 

Ans. In this type the small light coil of wire is sus- 
pended by a fine bronze wire between the poles of a station- 
ary magnet. 

988. How are the readings taken from these instru- 
ments ? 

Ans. From a circular scale, over which the needle of 
the instrument swings. 

989. "What is the purpose of recording instruments 
in electrical work? 

Ans. They are designed to record on a chart a con- 
tinuous indication of the successive instantaneous 
values of all quantities such as current, pressure, 
power, frequency power factor, etc. 

990. How are electric recording instruments classi- 
fied? 

Ans. Into two general classes, viz: direct acting 
type and the relay type. 

991. Describe the action of the direct acting type. 
Ans. The moving element of the meter carries the 

pen or tracing point and causes it to move over a 
properly ruled chart which is driven at a constant 
speed, by a suitable clockwork. 

992. On what principle does the relay type of re- 
cording meter operate? 

Ans. The moving element of the meter operates a 
set of contacts which close an auxiliary circuit. This 
auxiliary circuit contains the solenoids which operate 



166 Steam Engineering 

the pen, therefore the accuracy of the record is not 
affected by a change in friction of the pen. 

993. Which type of recording meter may be con- 
sidered the more accurate? 

Am. The relay type. 



i ! 



Definitions 

A 

A. C. — Alternating Current. 

Absorption. — The act of one form of matter sucking, or 
draining in some other form of matter, as in the case 
of a sponge taking up water. 

Acceleration. — The increase of motion. 

Accumulated Electricity. — Electricity confined or stored, 

as in a condenser. 

Accumulator. — Sometimes used to designate a condenser, a 
Leyden jar, or a storage battery. 

Active Coil. — A coil or conductor conveying a current of 
electricity. 

Active Current. — The active constituent of an alternating 
current, in contradistinction from the wattless compo- 
nent. 

Active Wire. — The section of wire on the armature of a 
dynamo which goes through the field of force, in con- 
tradistinction from the remaining wire, which does not 
pass through the flux. 

Aerial Circuit. — An elevated circuit. 

Air Blast. — A blast of air acting upon the surface of a 
commutator to prevent damaging flashes. Also used to 
cool transformers in some cases. 

Air Gap. — Any gap or aperture in a circuit which con- 
tains air only. 

Air Insulation, — Insulation produced by the action of air. 

167 



168 Steam Engineering 

American Wire Gauge. — The name by which the Brown & 
Sharpe wire gauge is known, in which the diameter of 
the largest wire. No. 0000, is 0.46 inches, and wire No. 36, 
0.005 inches, and all other diameters progress in geomet- 
rical order. 

Ammeter. — An abbreviation for ampere meter. Used for 
measuring current rate, or volume. Any calibrated gal- 
vanometer having its scale marked to read amperes is 
an ammeter. 

Ampere. — The unit of electric current flow. An ampere is 
that volume of current which would pass through a cir- 
cuit that offered a resistance of one ohm under an electro- 
motive force of one volt. 

Ampere Hour. — A unit of quantity equal to the amount of 
electricity transmitted by one ampere flowing during one 
hour. 

Ampere Turn. — A unit of magneto-motive force equal to 
the force resulting from the passing of one ampere over a 
single turn of wire. 

Anode. — The positive pole a battery. 

Arc. — A segment of a circle. A voltaic arc. 

Armature Eeaction. — The reactive magnetic effect result- 
ing from the action of the current in the armature of a 
dynamo on the magnetic circuit of the machine. 

B 

B. S. G. — British standard gauge. 

B. & S. W. G. — Brown & Sharpe wire gauge. 

B. W. G. — Birmingham wire gauge. 

Balanced Load. — A load uniformly apportioned to two or 

more generators. 
Balanced Eesistance. — A resistance arranged in a bridge, 

and balanced by the residuary resistance in the bridge. 



Definitions 169 

Bar Windings. — Armature windings constructed of copper 
bars. 

Bipolar. — Possessing two poles. 

Birmingham Wire Gauge. — A wire gauge used in England. 

Booster. — An auxiliary dynamo used to increase the volt- 
age of a feeder, or a set of feeders beyond the voltage of 
the rest of the system. 

Bridge, Electric. — A contrivance used to measure unknown 
resistances by comparison with adjustable ones. 

Bunched Cable. — A cable having more than one wire, or 
conductor. 

Bus-bars.— Bars composed of heavy conducting metal, and 
connected directly with the poles of generators. 

C 

C. G. S. — Centimetre, Gramme, second. 

C. P. — Candle power. 

Calibrate. — To ascertain the complete or relative values of 
the indications of electrical measuring instruments. 

Candle. — The unit of photometric energy. Equals the light 
produced by a standard candle burning at the rate of two 
grains per minute. 

Cathode. — Opposed to anode. 

Condenser. — A device for augmenting the capacity of an 
insulated conductor by placing it in contiguity to another 
earth-connected conductor, but from which it is sep- 
arated by an intervening body which will permit electro- 
static induction to occur through it. 

Constant Current. — A current, the strength of which does 
not vary. 

Continuous Current. — A current flowing in the same di- 
rection only. 

Cycle of Alternations. — Alternations of the current per 

second. 



^ 



170 Steam Engineering 

Coulomb. — The unit of electric quantity accepted for prac- 
tice. That quantity of electricity that would pass in one 
second through a circuit conveying one ampere. That 
quantity of electricity contained in a condenser of one 
Farad capacity when subjected to an E. M. F. of one 
volt. 

D. 

D. C. — Direct current. 

D. P. S. — Double pole switch. 

Differential Winding. — Double winding of magnet coils 
resulting in the opposition of the two poles to each other. 

Dynamic Electricity. — Current electricity as distinguished 
from static electricity. 

Dyne.— The C. G. S. unit of force. 

E 

E. H. P. — Electrical horse-power. 
E. M. F. — Electromotive force. 

Electrolysis. — Chemical decomposition by the action of an 
electric current. 

F 

Farad. — The practical unit of electrical capacity. That 
capacity of a conductor that is capable of holding one 
coulomb at one volt potential. 

Feeders. — Wires furnishing the main conductors with cur- 
rents at different points, thus serving to equalize the po- 
tential under load. 

Five-wire System. — A system wherein four series connected 
dynamos are connected to five conductors. 

Flux. — Magnetic induction; the number of lines of force 
which pass through a magnetic circuit. 

Frequency. — Number of cycles per unit of time by an al- 
ternating current. 



Definitions 171 

G 

Gramme. — A unit of weight equal to the weight of one cubic 
centimetre of pure water at its maximum density, at a 
temperature of 39.2° Pahr. in a vacuum. A weight 
equal to 15.44 grains troy. 

H 

H. P. — Horse-power. 

Hard-drawn Copper Wire. — Copper wire hardened without 
annealing, by being drawn several times. 

Henry. — The practical unit of electro-magnetic, or mag- 
netic inductance. 

Horse-power, Electric. — A rate of electrical work equal to 
746 watts, or 746 volt-coulombs per second. 

Hysteresis. — Slowness of magnetization in respect to mag- 
netizing force. 

I 

Induction. — The influence exerted without contact, by a 

magnetic field, or a charged mass upon neighboring 

bodies. 
Inverted Arc Lamp. — An arc lamp wherein the positive 

carbon is below instead of above, as in the regular arc 

lamp. 

J 

Jump Spark. — A disruptive spark excited between two con- 
ductors, in distinction from a spark excited by a rubbing 
contact. 

K 

K. W.— Kilowatt. 
Kilowatt. — One thousand watts. 

Kilowatt-Hour. — Work equal to the expenditure of one K. 
W. in one hour. 



172 Steam Engineering 

L 

Lag. — Dropping behind. 

Lagging of Current. — The retarding in phase of an al- 
ternating current behind the pressure which produces it 

M 

Megohm. — One million ohms. 

Metre. — A measure of length equal to 39.368 inches. 

Miero-Farad. — The millionth of a Farad. 

Mil. — One thousandth of an inch. 

Multiphase. — Containing more than one phase. 

Multiple Circuit. — A circuit in which the positive poles of 
a number of separate sources, and receptive devices are 
connected to a single positive lead or conductor; their 
negative poles being connected to a single negative lead 
or conductor. 

Multiple Series. — Series groups connected in multiple. 



Ohm. — The practical unit of resistance. A resistance that 
would confine the electric flow under an electromotive 
force of one volt to a current of one ampere, or one cou- 
lomb per second. 

Ohm's Law. — The basic law, expressing the relation be- 
tween current, E. M. F., and resistance in active cir- 

E 
cuits. Expressed algebraically 1= — , in which I equals 

E 

current intensity, E equals E. M. F. ? and E equals resist- 
ance. Other forms of expressing ohms law are as follows : 

E 
E=— . B=BL 

I 



Definitions 173 

Over Compounded. — Compound winding of such a charac- 
ter on a dynamo that its voltage at its terminals is caused 
to increase under a greater load. 

P 

Parallel Circuit. — A term signifying multiple circuit. 

Parallel Series. — Signifies a multiple series connection. 

Periodicity of Alternation. — The rate of succession of al- 
ternations per second, or per minute. The frequency. 

Polyphase Current. — Currents that constantly differ from 
each other, due to their proportion of periods of alter- 
nation, and adapted to polyphase motors. 

Proposed Definition for 2,000 Candle Power. — An arc 
whose maintenance will require 450 watts. 

E 

Rheostat. — Will adjust the resistance without opening the 
circuit. 

S 

Standard Ohm. — A piece of pure copper wire one circular 
mil in diameter, and one foot long at a certain tempera- 
ture. 

Static Electricity. — Electricity generated by friction. 

V 

Volt. — The practical unit of electromotive force. An E. 
M. F. that would cause a current of one ampere to flow 
through a resistance of one ohm. 

W 

Water Horse-Power. — The power developed by 15 cubic feet 
of water falling through a distance of one foot per second. 

Watt. — The practical unit of electric activity, rate of work, 
or energy. A watt equals 44.25 foot pounds of work done 
per minute, or 0.7375 foot-pounds of work done per sec- 
ond. 

Watt-Hour. — Unit of electric work. One watt exerted or 
expended for one hour. 



INDEX 

A 

Absolute Pressure 57 

Absolute Zero 40 

Absorption System of Refrigeration 97-9S 

Acceleration of Gravity 25 

Adiabatic Curve . 58-59 

Air Compressors 85-89 

Air Compression at High Altitudes 88 

Air Compression — Methods of 85, 86, 87 

Air Required for Combustion 33 

Alternator 114 

Alternating Current 111-118 

Ammeter 161 

Ampere 108-161 

Angular Advance 52 

Anhydrous Ammonia 93-94 

Armature Construction 121-148 

Armature Troubles 148-152 

Armature Winding 133-148 

Atlas Water Tube Boiler 12-13 

B 

Babcock and Wilcox Boiler 8-9 

Back Pressure 57 

Bigelow Hornsby Boiler 10-11 

Blow Off Pipe and Cock 22-27 

Boiler Material 15 

Boiler Setting and Equipment 19-25 

Boyles Law 58 

Brick for Boiler Setting 19 

Brine System of Refrigeration 96-97 

Brushes— How to Set 151-152 

Buck Stays 20 

Bursting Pressure — Rule for . 18-37 



Index 

C 

Caiurtl Water Tube Boiler ?-S 

Calculating Pump Capacity 24-25 

Calorific Valve of Fuel .40 

Calorimeter 44 

Care and Operation of Boilers 31-33 

Causes of Poor Combustion 38 

Chimneys 29 

Circuit Breaker 163 

Classes of Mechanical Stokers 28 

Cleaning Fires 31-32 

Coal — Composition of 39 

Combustion Chamber 6, 7, 20 

Combustion— Heat 39-42 

Compound Dynamo 116 

Compression 52-54 

Compound Engines 47, 49-50 

Condensers ■ . . 48, 75-76 

Condensing Engine * 47 

Condenser Pressure 57 

Conservation of energy 107 

Coulomb 108-161 

Co 2 — Meaning of 39 

Curtis Steam Turbine 71-72 

Current Phase 120 

Cut-off . . . . 53-54 

D 

Dead Center 54 

Direct Current .111-117 

Dished Heads 17 

De Laval Steam Turbine 72-73 

Definitions — Electric 167-173 

Definitions — Steam 57-59 

De Lavergne Ice Machine 96 

Domes and Mud-Drums 22 

Draft Gauge 44 

Drum Winding 115 

Dry Air Pump 76 

Duplex Water Tube Boiler 13-14 



Index 

Duties of an Engineer 31-32 

Dynamics 59 

Dynamo-Principle of 110-111 

Dyuamo — Construction 112-114 

Dynamotor 154 

E 

Eccentric 52-53 

Economizers 40 

Efficient Joint 16 

Electricity for Engineers 107-165 

Electric Circuit 110 

Electric Motor 116-117 

Elevators — Electric and Hydraulic 99-105 

Erie City Water Tube Boiler 14 

Equivalent 46 

Evaporation Tests 43-46 

Exhaust Injector 28 

Expansion Curve 59 

F 

Factor of Safety 18 

Failure of Joints • 16-17 

Feed Pipes 23 

Feed Pumps 22-24 

Feed Water Heaters 22, 27-29 

Field Rheostat 114 

Flue Gas Analysis 45 

Foaming 34 

Force 59 

Former Coils 143 

Friction— Laws of 65-66 

Frequency — Electric 162 

Fusible Plugs 21 

G 

Galvanometer 164 

Gas Engines 77-83 

Gas Engine Indicator S3 

Gas Engine Igniter 82 



Index 

Gas Producers 83 

Gauge Pressure 57 

Governor 55 

Grate Surface 20 

Grounded Circuit 150 

Gusset Stays 17 

H 

Hamilton-Holzwarth Steam Turbine 73-74 

Heat . . . ^ 40 

Heat Unit 41 

Heine Water Tube Boiler 8 

Horizontal Tubular Boiler 5 

Horse Power . . . . 58 

Hydraulic Elevator s . .100-105 

I 

Imperfect Combustion 33 

Indicator 61-63 

Indicated Horse Power 58 

Induction — Laws of 110 

Ingersoll-Rand Air Compressor 88-89 

Initial Pressure 57 

Injector 23-24 

Isothermal Curve 59 

J 
Joule 10S 

K 
Kilo- Watt ........ Ill, 161 

L 

Lap 53 

Latent Heat 41 

Lead 52-55 

Lightning Arresters 164-165 

Linde Ice Machine 95 

Low Water — What to do in Case of „ , 34 

Lubrication 65-67 



Index 

M 

Magnet , 10s 

Magnetic Circuit 110 

Marzolf "Water Tube Boiler 13 

Maxim Water Tube Boiler 9-10 

Mean Effective Pressure 58 

Mechanical Draft — Systems of 28-29 

Mechanical Equivalent of Heat 41 

Mechanical Stokers 28-29 

Momentum 59 

Motion — First Law of 59 

r Arma tures 140-148 

O 

Ohm 108-161 

Ohm's Law 161 

Oil Switches 163 

Open Circuit 151 

Otis Geared Traction Elevator 99-101 

Otis Traction Elevator 99 

P 

Piston Displacement 5S 

Piston Speed 58 

Pitch of Boiler Rivets 15-lfi 

Pop Valve 21 

Potential 110 

Power 59 

Principles of Boiler Construction 14 

R 

Radius of Eccentricity 52 

Ratio of Expansion 5? 

Bateau Steam Turbine 74 

Reidler-Stumpf Steam Turbine 74-75 

Refrigeration 91-S8 

Ring Winding 115 

Rotary Converters 154-162 

or Firics 31-32 



Index 

s 

Safety Valves S3 

Series Dynamo 116 

Short Circuit — How to Locate 150-151 

Shunt Dynamo 115 

Simple Engine 47 

Specific Heat 41 

Steam 41-42 

Steam Engines . . 47-70 

Steam Gauge V 21 

Steam Headers 24 

Steam Turbines 69-76 

Switch Boards 159-164 

Synchronizer 158 

T 

Tensile Strength 14-15 

Terminal Pressure 57 

Theoretical Duty of Steam 59 

Thermodynamics — First Law of 59 

Thermodynamics — Second Law of 91 

Through Stay Rods 17 

Total Heat of Evaporation 46 

Tra nsf ormers 153-154 

Triumph Ice Machine 96 

Types of Boilers • 5 

Types of Valves , . . 51 

U 

Unit oC Work '. 108 

Unit of Power 10S 

V 

Vacuum 58 

Valve Travel 52 

Valves and Valve Setting 51-56 

Valves for Boiler Connections 24 

Volt 108, 161 



Index 

W 

Washing Out Boiler 35-36 

Water — Composition of 41 

Water Column 20-21, 36 

Water Tube Boiler 5-6 

Watt .108-109 

Watt Meter 161 

Westinghouse-Parsons Steam Turbine 71 

Wickes Water Tube Boiler. . . 11-12 

Work 59 



Jf - 



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